R v Secretary of State for Transport, ex parte Richmond upon Thames London Borough Council and others

Transcript date:

Wednesday, September 29, 1993



High Court

Judgement type:



Laws J

R v Secretary of State for Transport, ex parte Richmond upon Thames London Borough Council and others


[1994] 1 All ER 577, [1994] 1 WLR 74




Air traffic - Noise nuisance - Landing and take-off - Restrictions on landing and taking off to avoid, limit or mitigate noise - Secretary of State empowered to specify maximum number of aircraft movements - Secretary of State proposing to impose noise quota restrictions on aircraft operators - Operators free to choose what aircraft movements would make up alloted quota by using greater number of quieter aircraft or lesser number of noisier aircraft - Whether Secretary of State's proposals invalid - Civil Aviation Act 1982, s 78(3).

Administrative law - Legitimate expectation - Right to be heard - Consultation - Whether doctrine of legitimate expectation giving rise to enforceable expectation that existing policy will not be changed even though those affected were consulted.


Under s 78(3) [a] of the Civil Aviation Act 1982 the Secretary of State was empowered, for the purpose of avoiding, limiting or mitigating the effect of noise and vibration connected with the taking off or landing of aircraft at designated airports, to prohibit aircraft of specified descriptions from taking off or landing or to specify the maximum number of occasions on which such aircraft could take off or land during certain periods. In 1988 measures were introduced restricting night movements by aircraft at London's major airports by reference to the number of take-off and landing movements permitted at night. Those restrictions were due to expire in October 1993 and it was the Secretary of State's intention, having regard to the desirability of encouraging airlines to use modern quieter aircraft, to replace the restrictions based on the number of individual aircraft movements permitted by new restrictions based on a quota system whereby aircraft were assigned a quota count according to their noise levels and operators would be free to choose what aircraft movements would make up their alloted quota, ie by using a greater number of quieter aircraft or a lesser number of noisier aircraft. The applicant councils, which were the local authorities for the areas around the three main London airports, sought judicial review of the Secretary of State's decision to introduce the new restrictions, claiming that the inhabitants of their areas would be adversely affected by the new restrictions because they would not lessen the numbers or noise of aircraft taking off and landing at night but would merely spread the noise between a greater or lesser number of aircraft movements and could potentially increase noise levels at the airports.

a Section 78(3), so far as material, is set out at p 580 d to g, post

Held - The Secretary of State's decision to introduce new restrictions for night flying over the three main London airports based on a quota system according to the noise of the aircraft used was contrary to the terms of s 78(3)(b) of the 1982 Act because the new restrictions did not 'specify the maximum number of occasions on which aircraft of descriptions so specified may be permitted to take off or land' as required by s 78(3)(b) but only sought to impose control by reference to levels of exposure to noise. Accordingly, although the Secretary of State had intended to act within the purpose of s 78(3), he had done so by an impermissible method. His decision was therefore invalid and a declaration would be made to that effect (see p 591 j to p 592 h and p 593 j to p 594 a f g, post).

Per curiam. (1) Although the doctrine of legitimate expectation may require a public authority not to change its existing policy without giving those affected a right to be heard, the dotrine does not extend to give rise to an enforceable substantive expectation that a policy will not be changed even though those affected have been consulted (see p 595 c to g j to p 596 b, post); R v Secretary of State for the Home Dept, ex p Khan [1985] 1 All ER 40 and R v Secretary of State for the Home Dept, ex p Ruddock [1987] 2 All ER 518 considered.

(2) There is a pressing need for RSC Ord 53 to be amended to allow the court to refuse leave to apply for judicial review on some grounds, while granting it on others, as the court's view of the application's merits dictates, so that the court hearing the substantive application is not required to consider points which were unarguable and ought not to have attracted leave (see p 600 h j, post).



For noise and vibration caused by aircraft, see 2 Halsbury's Laws (4th edn reissue) para 1185.

For the Civil Aviation Act 1982, s 78, see 4 Halsbury's Statutes (4th edn) (1987 reissue) 201.


Cases referred to in judgment

Associated Provincial Picture Houses Ltd v Wednesbury Corp [1947] 2 All ER 680, [1948] 1 KB 223, CA.

Council of Civil Service Unions v Minister for the Civil Service [1984] 3 All ER 935, [1985] AC 374, [1984] 3 WLR 1174, HL.

CREEDNZ Inc v Governor General [1981] 1 NZLR 172, NZ SC.

Findlay v Secretary of State for the Home Dept [1984] 3 All ER 801, [1985] AC 318, [1984] 3 WLR 1159, HL.

Liverpool Taxi Owners' Association, Re [1972] 2 All ER 589, sub nom R v Liverpool Corp, ex p Liverpool Taxi Fleet Operators' Association [1972] 2 QB 299, [1972] 2 WLR 1262, CA.

R v Board of Inland Revenue, ex p MFK Underwriting Agencies Ltd [1990] 1 All ER 91, [1990] 1 WLR 1545, DC.

R v Jockey Club, ex p RAM Racecourses Ltd [1993] 2 All ER 225, DC.

R v Secretary of State for the Home Dept, ex p Khan [1985] 1 All ER 40, [1984] 1 WLR 1337, CA.

R v Secretary of State for the Home Dept, ex p Ruddock [1987] 2 All ER 518, [1987] 1 WLR 1482.


Application for judicial review

Richmond upon Thames London Borough Council, Windsor and Maidenhead Royal Borough Council, Tandridge District Council, Hillingdon London Borough Council and Slough Borough Council applied, with the leave of Sedley J given on 30 July 1993, for judicial review of the decision of the Secretary of State for Transport, announced by a press release on 6 July 1993, to introduce new night flying restrictions based on a noise quota system to restrict noise at Heathrow, Gatwick and Stansted Airports. The relief sought was (i) an order of certiorari to quash the decision, (ii) further or alternatively, an order of mandamus requiring the Secretary of State to reconsider his decision and to exercise his powers under s 78 of the Civil Aviation Act 1982 according to law, (iii) further or alternatively, an order of mandamus requiring the Secretary of State to extend the existing restrictions in relation to the three airports for such period as he considered necessary to enable him to reconsider the exercise his powers under s 78 of the Civil Aviation Act 1982 according to law, (iv) further or alternatively, an order of prohibition restraining the introduction of the new restrictions, and (v) further or alternatively, a declaration that the new restrictions were unlawful. The facts are set out in the judgment.


Richard Gordon (instructed by Richard Buxton, Cambridge) for the applicants.; Ian Burnett and Mark Shaw (instructed by the Treasury Solicitor) for the Secretary of State.


Cur adv vult

29 September 1993. The following judgment was delivered.

29 September 1993





On 6 July 1993 the Secretary of State for Transport announced his intention to introduce in October 1993 what is described in his press notice as 'A tough new quota system of night flying restrictions to reduce noise at Heathrow, Gatwick and Stansted'. The decision to introduce these measures is the subject of the judicial review now before me. Sedley J gave leave on 30 July 1993. The applicants are a number of local authorities for the areas around each airport. They say that their constituents, or inhabitants, will be adversely affected by the new regime if it comes into force. The respondent is of course the Secretary of State.

Restrictions against night movements by aircraft at Heathrow have been in effect since 1962. Most recently a set of measures was introduced in 1988 which covered both Heathrow and Gatwick. Although, as I understand it, it has been updated from time to time, the regime of 1988 at present remains in force, but it is due to expire in October 1993, and it is the Secretary of State's intention to substitute his new measures (which will for the first time impose restrictions at Stansted) with effect from 24 October. Put simply, the existing means of control involves a direct limitation upon the number of take-off and landing movements permitted at night. Shorn of certain detailed qualifications which do not matter for present purposes, the number of such movements presently allowed at Heathrow is 5,750 per year.

The Secretary of State's new proposals, however, take a different form. At this stage I shall give only a crude description; it will be necessary to refine it later. A quota count (QC) is to be assigned to each aircraft type. Each QC consists of a number of units from 0 5 to 16. In simple terms, the higher the QC, the noisier the aircraft. A given number of quota points will be assigned to each airport (12,000 in the case of Heathrow: 7,000 for the summer season, 5,000 for the winter). Aircraft movements which would produce any excess over the quota limit will be prohibited. The difference between the old system and the new system is therefore this: whereas at present, night flying restrictions are achieved by reference to an express specification of the number of the individual aircraft movements permitted, hereafter it will be done by reference to the permitted maximum number of quota points, and this means that within the ceiling defined by the maximum quotas, the aircraft operators will be free to choose how the quota is to be distributed between noisier and less noisy aircraft; they may operate a greater number of quieter aeroplanes, or a lesser number of the noisier types.

The decision of July 1993 followed widespread consultation which had been initiated by a consultation paper of January 1993 issued by the department. And in December 1992 the department had published a research paper with the title 'Report of a Field Study of Aircraft Noise and Sleep Disturbance'. There had been a final draft report the previous month, which is also among the papers before the court. These documents are of some importance for certain aspects of Mr Gordon's argument, as are the terms of a consultation paper of November 1987 and a press notice of 10 February 1988, which preceded the institution of the 1988 restrictions.

I must canvass the facts more closely, but will first set out the statutory provision under which the Secretary of State proposes to act and which, indeed, authorises the 1988 measures now in force. This is of obvious importance because Mr Gordon has submitted that the Secretary of State's scheme would be illegal because the statute on its true construction confers no power to give effect to it. The relevant provision is s 78(3) of the Civil Aviation Act 1982:

'If the Secretary of State considers it appropriate, for the purpose of avoiding, limiting or mitigating the effect of noise and vibration connected with the taking off or landing of aircraft at a designated aerodrome, to prohibit aircraft from taking off or landing, or limit the number of occasions on which they may take off or land, at the aerodrome during certain periods, he may by a notice published in the prescribed manner do all or any of the following, that is to say-(a) prohibit aircraft of descriptions specified in the notice from taking off or landing at the aerodrome (otherwise than in an emergency of a description so specified) during periods so specified; (b) specify the maximum number of occasions on which aircraft of descriptions so specified may be permitted to take off or land at the aerodrome (otherwise than as aforesaid) during periods so specified; (c) determine the persons who shall be entitled to arrange for aircraft of which they are the operators to take off or land at the aerodrome during the periods specified under paragraph (b) and, as respects each of those persons, the number of occasions on which aircraft of a particular description of which he is the operator may take off or land at the aerodrome during those periods ...'

Given the course of the argument before me it is convenient also to read sub-s (5)(c):

'if it appears to the Secretary of State that an aircraft is about to take off in contravention of any prohibition or restriction imposed in pursuance of that subsection, then ... any person authorised by the Secretary of State for the purpose may detain the aircraft for such period as that person considers appropriate for preventing the contravention ...'

I return to the facts. There is first some material whose primary relevance is to Mr Gordon's submission that there was a change of policy in 1988 which ought to attract legal consequences. The consultation paper issued on 6 November 1987 contained a number of statements concerning the policy of the government as regards the improvement of what was called the 'night noise climate' at Heathrow (the paper before me related only to Heathrow Airport). I need not read all of the citations relied on by Mr Gordon. It is enough to quote from para 4:

'The restrictions as revised in 1981 phased out night flights by the older, noisier aircraft. This, and the airlines' investment in newer and quieter aircraft, has over the years brought about an improvement in the night noise climate around Heathrow. That is a significant achievement which we must not throw away. We are therefore determined to ensure that this improvement continues ... the objectives which underlie the proposals in this Paper are therefore:-to continue to improve the night noise climate so that disturbance of people's sleep is further reduced [and] to encourage airlines to continue to invest in quieter, modern aircraft.'

And para 5:

'We believe that people living around the airports should continue to benefit from the advances in aircraft design and technology which are producing quieter aircraft. At the same time we want to avoid unnecessary regulation.'

The consultation paper indicated (para 34) that the new restrictions then envisaged would be fixed for at least five years. There followed a press notice of 10 February 1988 announcing the new restrictions which the Secretary of State after consultation had decided to impose. Statements in this documet are also relied upon by Mr Gordon. It related to night flying both at Heathrow and Gatwick. It quoted a parliamentary answer given by the Secretary of State, in which he said (127 HC Official Report (6th series) written answers cols 247-248):

'On 6th November last year I published proposals for future night restrictions at the two airports. I set out then my objective-to improve the night noise climate around the airports without imposing unnecessary restrictions on the airline industry ... The challenge is to ensure that the benefits of modern aviation technology are enjoyed not only by those who fly, but also by those on the ground. I believe we can do that by giving airlines an incentive to replace their older, noisier aircraft by modern, quieter ones ...'

That, then was the government's position in 1987-88, and the 1988 restrictions were duly introduced. Mr Gordon says that the documentation discloses a clear assurance or undertaking by the department that from 1988 onwards it would promote a continuing reduction in aircraft noise effects. It is common ground-and this is important for Mr Gordon's argument-that by 1993, owing to the increased use of quieter aircraft, the night noise climate at the airports had indeed improved since 1988.

Although chronologically other significant events, relevant to other parts of the case, intervene-the publication of the final draft and the report of the field study in November and December 1992-it is convenient to turn to the consultation paper of 1993 to see the terms in which the department, in proposing the new regime, recorded and reflected its policy of 1988, and set out its aspirations in 1993. Paragraph 34 of the paper is in these terms:

'Since 1988, more of the quieter types of aircraft have been acquired by airlines, improving the night noise climate. In keeping with the undertaking given in 1988 not to allow a worsening of noise at night, and ideally to improve it, it is proposed that the quota for the next five years based on the new quota system should be set at a level so as to keep overall noise levels below those in 1988. For Heathrow the proposed summer noise quota is 7,000 and for Gatwick 9,000. The 1988 summer quota for Heathrow would have been about 8,000 if calculated on the new basis, and the summer quota for Gatwick about 11,450.'

Mr Gordon says that this paragraph misdescribes the government's policy assurances of 1988. He says there is a difference of no little importance between an assurance 'to improve the night noise climate' and an undertaking 'not to allow a worsening of noise at night, and ideally to improve it'. He says that the position is the more stark since it has been government policy at least since 1981 to encourage airlines to use quieter aircraft and to confer the benefit of the consequent lower noise levels upon the public. Yet, so the submission goes, para 34 of the 1993 consultation paper indicates no more than an intention to keep overall noise levels below those of 1988; that, he says, is a departure from the announced policy, not a continuation of it. And when, after consultation, the new quota system was formally announced by the press notice of 6 July 1993, it was made clear that this was indeed the thrust of the policy. The notice said:

'The main points are ... the quota levels at Heathrow and Gatwick are designed to keep overall noise levels below those in summer 1988 when the current restrictions were introduced.'

He developed this part of the case alternatively by reference to the doctrines of legitimate expectation and Wednesbury principles (see Associated Provincial Picture Houses Ltd v Wednesbury Corp [1947] 2 All ER 680, [1948] 1 KB 223). I shall deal with these and his other submissions when I have set out the other principal facts necessary for my decision.

It is appropriate next to go back to November 1992, when the final draft of the department's field study report came into existence, and to December, when the report was itself published. These documents are important for what Mr Gordon called 'the sleep prevention issue'. One starts with the perhaps obvious proposition that while being awoken from sleep is one problem, being prevented from getting back to sleep, or from falling asleep in the first place, is another. 'Sleep arousal' is to be distinguished from 'sleep prevention'. Mr Gordon says that 'sleep prevention' was not addressed in the final draft or report although there are passages in the report suggesting that there may be an important relationship between aircraft noise and sleep prevention, as to which further research was required. Notwithstanding that, the argument continues, the department treated the report as justifying a belief that no further research work on sleep prevention would undermine the report's conclusion that aircraft noise was not a significant problem. It is submitted that that is a view which could not rationally be arrived at on the material before the Secretary of State. At this stage, therefore, I should examine some of the detail and explain the way in which the Secretary of State has made use of the report.

I need not take much time with the final draft as opposed to the report itself. But I should notice para 33 of the introductory summary in the draft:

'These conclusions are based on measurements of arousals from sleep. Until further analysis is complete, few supportable observations can be made about the possible effects of noise in preventing sleep onset at the beginning of the night, or delaying return to sleep after awakening, during the night, or in the early morning.'

In the report itself, this paragraph has in effect been substituted by the following (para 34):

'Work is continuing on a number of detailed points to supplement findings in this report including further analysis of the possible effects of noise in preventing sleep onset at the beginning of the night, or delaying return to sleep after awakening during the night or in the early morning. This will not change the conclusions about aircraft noise presented here but additional results will be published subsequently.' (My emphasis.)

The full title of the report is 'Report of a Field Study of Aircraft Noise and Sleep Disturbance'. It includes a glossary and definition of terms. One of the terms defined is 'Disturbance':

'"Sleep Disturbance" can be defined in a variety of ways. In this report the expression is used generally to cover both awakenings and actimetrically determined arousals; however, it is also used in a more specific sense to describe events of particular significance such as EEG-awakenings which, if experienced often enough, could have longer term consequences.'

Paragraph 2 of the summary in the report sets out the objectives of the study. They-

'were to determine: (a) the relationships between outdoor aircraft noise levels and the probability of sleep disturbance, (b) the variation of these relationships with time of night.'

Paragraph 5.2 of the report is in these terms:

'The main question to be addressed is, "does aircraft noise cause sleep disturbance within sleep itself?" This is distinct from the questions of: (a) whether such noise at bedtime interferes with the process of getting to sleep, or (b) whether such noise causes premature awakening at the end of sleep. Data gathered during this study may well throw light on these latter questions, which are the subject of continuing analysis. The results presented here are mainly concerned with the primary line of inquiry.'

These references (and others also were relied on by Mr Gordon) appear to demonstrate that the report was indeed primarily concerned with the effects of aircraft noise upon persons already asleep and not with its effects upon people trying to get to sleep. However, incorporated into the report were the results of an extensive social survey in which questionnaires were administered, one of which sought to ascertain the percentage of respondents giving aircraft noise as the main reason for having difficulty in getting to sleep, and another to identify the percentage giving aircraft noise as the main reason for having difficulty getting back to sleep, once awakened. Those percentages are plotted in figures 35 and 37 which are appended to the report. These figures also contain, for comparison purposes, the effect of the answers to very similar questionnaires administered in the course of sleep surveys carried out by the Civil Aviation Authority in 1980 and 1984. Paragraph 4.2 of the report says:

'The wording of the questions in the 3 questionnaires [the third-figure 36-concerns being awakened from sleep] was very similar and the responses clearly exhibit similar trends, albeit with the large scatter typical of social survey data ... there are similar degrees of agreement in all three cases suggesting that, in relation to night noise exposure in Leq, general perceptions of night time aircraft noise effects have changed little since 1980.'

No doubt this entitled the Secretary of State to conclude that the ratio of people complaining about aircraft noise waking them up to those complaining that aircraft noise stopped them getting to sleep had remained roughly constant since 1980. And the figures, into whose detail I need not travel, show that the reported incidence of aircraft noise causing difficulty in getting to sleep was no greater than that of aircraft noise induced awakenings.

Given this material, I turn to the evidence of the Secretary of State's decision-making process, so far as relevant to Mr Gordon's 'sleep prevention issue'. It is essentially contained in the affidavits of Miss McWatt and Dr Ollerhead. At para 20 of her affidavit Miss McWatt says:

'Paragraph 34 of the report is intended to say that the results of additional work will supplement the report's conclusions, not replace them. [A citation from the preface to the summary of the report is then set out, and is said to reinforce the proposition just stated.] The reasons why, as a matter of scientific technical analysis, the report was able to be confident that any further work on "sleep prevention" (as distinct from arousal from sleep) would not undermine its conclusion that aircraft noise was not a significant problem are set out by Dr Ollerhead in his affidavit ...'

In para 21 she says:

'Sleep disturbance including "sleep prevention" was considered in the report. The Secretary of State accepted the conclusions in the report including paragraph 34 and was aware that the social survey data in figures 35 to 37 effectively showed no change in respect of difficulties of getting to sleep ("sleep prevention") from previous studies.'

I shall come to Dr Ollerhead's evidence in a moment. But I can identify at once the proposition advanced by Mr Gordon in reliance on the affidavit of Miss McWatt. She asserts on behalf of the Secretary of State that the report 'was able to be confident that any further work on "sleep prevention"... would not undermine its conclusion that aircraft noise was not a significant problem'. This is not what the report says. Paragraph 34 of the summary, which I have quoted, asserts in effect that further work, which would include analysis of sleep prevention, will not change the conclusions about aircraft noise arrived at in the report. But on the face of it, so it is submitted, this is not a proposition of substance, but a truism which could carry the decision-making process nowhere: not least, given the clear definition of 'disturbance' in the report, the conclusions reached only related to sleep arousal. Logically, they would of course be untouched by the results of any further work upon the different problem of 'sleep prevention'.

Dr Ollerhead in his first affidavit says at para 19(c):

'The report does not specifically address the question of "sleep prevention", as it makes clear. However, since, as figures 35-37 show, the reported incidence of aircraft noise causing difficulty in getting to sleep (in the first place or after awakening) is no greater than that of aircraft noise induced awakenings, it may reasonably be inferred from the subjective data that "sleep prevention" is no more of a problem than "sleep disturbance".'

It is not asserted on behalf of the Secretary of State, either here or anywhere, that there may not be a significant relationship at all between aircraft noise and sleep prevention. I need not, I think, therefore travel through the references in the report upon which Mr Gordon relies as establishing such a possibility. Nor, as I understand it, is it suggested for the Secretary of State that further scientific work upon the possible impact of aircraft noise on persons trying to get to sleep is unnecessary or undesirable. The questions which I will have to determine when I come to deal with the arguments upon this part of the case are in my judgment two. (1) Does para 20 of Miss McWatt's affidavit show that the Secretary of State misunderstood the report, so that his decision to introduce the new policy was based on demonstrably faulty reasoning, and so can be categorised as irrational? (2) Is the inference described by Dr Ollerhead at para 19(c), so far as it represents the Secretary of State's view (as to which I think there is no contest), one which is reasonably sustainable?

I should next notice a passage in para 7.6 of the report, because it is relevant to what Mr Gordon has described as 'the flight number issue'. The complaint is that the new quota system does nothing to regulate the frequency of flights at night (save that the overall permitted number of quota points at each airport implies in theory a maximum number of movements for each aircraft type or a set of maxima for any combination of aircraft types: this qualification is of great importance for the illegality issue upon s 78(3), but of no significance for immediate purposes): and that there is no material available to the Secretary of State to enable him to form a judgment as to the effects of a second aircraft movement, or successive movements, upon a person trying to get back to sleep; he should have equipped himself to form such a judgment, and given effect to it in his decision; so that the policy is irrational.

Paragraph 7.6 starts with the sentence:

'An important practical question, which is the subject of continuing analysis, concerns the possible effects of the time interval between successive ANEs [ANE is defined in the glossary as an 'Aircraft Noise Event; the noise experienced when a single aircraft passes by']; ie that shorter intervals might increase the probability of the second event causing arousal.'

Reference is then made to certain scientific work relevant to the question, and the paragraph continues:

'Thus it may be inferred that, if one ANE causes disturbance, this will increase to some extent the probability of disturbance by an immediately following ANE. However, as the independent probabilities of either noise causing disturbance are low, any additional disturbance attributable to repeated events is likely to be very small ... again, it has to be stressed that these observations relate to arousal from sleep. No conclusion can yet be stated about the possibility that a second ANE might impede return to sleep after an awakening. Whether or not this has an important bearing upon end-of-night sleep disturbance is a question still being examined.'

Mr Gordon relies upon the policy's theoretical potential for very large increases in flight movements, as, for example, would occur if all the aircraft using the airport at night were in the QC 0 5 category. There is evidence from Miss McWatt (para 16) that such a state of affairs is extremely improbable; she says that the major requirement for night movements at Heathrow is for Boeing 747s; they are QC 2 or 4 (some are QC 8 or 16, and aircraft of those latter quota counts cannot under the policy be scheduled to land or take off during night hours at all). There is no expectation of substantial changes or sudden increases in night movements at Heathrow. It is also the case that under the new policy fewer types of aircraft will be exempt altogether than under the existing system.

There is next a sentence in para 1.2 of the report relevant to Mr Gordon's 'health effects issue'. His complaint is that there is nothing to show that the government has given any consideration whatever to the question whether aircraft noise might affect the health of a person trying to get to sleep, or indeed while he remains asleep. The last subparagraph of para 1.2 states:

'In a small number of studies, the effects of a noise-disturbed night on the individual's performance the following day has been determined using, for example, reaction time tests. Little research appears to have been carried into the relationships between marked sleep disturbance and any chronic health effects.'

So, says Mr Gordon, it may be inferred that there is no work upon the relationship (if any) between sleep prevention and health effects: to say nothing of health effects caused by noise while the person still sleeps.

An affidavit was put in at a late stage (without objection from the Secretary of State) from the applicant's solicitor, Mr Buxton, exhibiting two articles by experts which include some material to suggest that health may be affected by noise during sleep: certainly that there may be physiological effects, such as an increased heart rate, and that there may be secondary effects, felt in the morning or day after the noise exposure. These, it is said, include increased fatigue.

I must next explain a concept not so far mentioned in this judgment, that of 'Leq'. As I will show, Leq is a defining factor in the new quota system, and Mr Gordon has submitted it was unlawful for the Secretary of State to lock his new proposals into this concept.

I may start with the definition of 'Leq' given in the glossary to the December 1992 report:

'A measure of long-term average noise exposure; for aircraft noise it is the level of a steady sound which, if heard continuously over the same period of time, would contain the same total sound energy as all the ANEs.'

I should next explain another concept, 'dB', also integral to the Secretary of State's proposed system. The glossary defines it in this way:

'Decibels, units of sound level, or relative sound level, calculated as 10 times the log (base 10) of a sound energy ratio. Used here to define differences between levels measured on the dBA scale.'

'dBA' is defined thus:

'Levels on a decibel scale of noise measured using a frequency dependent weighting which approximates the characteristics of human hearing. These are referred to as A-weighted sound levels; these are very widely used for noise assessment purposes.'

As the definition shows, Leq is a measure of average exposure to noise energy (as opposed to individual instances of subjective loudness); and that is the concept which the Secretary of State has deployed in the new scheme as the means of defining the limits of noise exposure which he wishes to enforce. Here I must refine the simple explanation of the scheme which I gave at the outset. What the Secretary of State has done is to arrive at a Leq value for the night period at each airport, summer and winter. That sets an average exposure to aircraft noise energy which is not to be exceeded. The quota points for individual aircraft types are then fixed by reference to international noise certification data. Each progression, from 0 5 to 1, 1 to 2, 2 to 4 etc, represents an increase of 3dB, which itself measures or implies a doubling of sound energy. The maximum quota points specified by the Secretary of State give effect to the Leq value determined by the Secretary of State for night periods during summer and winter at each airport.

Mr Gordon has submitted that Leq is an inherently unreliable measure of night-time noise. Its merits as such a measure are much in contention among the experts. I need not rehearse the various passages in the evidence in which conflicting views are canvassed, because it must be beyond argument that it is no part of my function to decide the merits of such a question. In my view the Secretary of State was plainly entitled in Wednesbury terms (and Mr Gordon's submission can only be based on Wednesbury) to take a measure of exposure to noise energy levels as his criterion for regulating aircraft noise at night. Whether in the end s 78(3) permits him to do so is of course another question. On this part of the case, there are really only two issues which require further consideration.

(1) Mr Gordon's submission that the government has itself accepted that Leq is an inherently unreliable measure, so that (as with the thirteenth chime of the clock) all their other protestations of its reliability are cast into doubt and one is left with nothing but a self-contradiction. Such a state of affairs might properly call for the court's intervention on Wednesbury grounds.

(2) His further submission that the 3dB progression does not at all represent the rate at which annoyance caused by noise, as opposed to noise energy level, is doubled; on the Secretary of State's own evidence, noisiness as such doubles in 10dB steps. Mr Gordon has also argued that at all events Leq as a measure of night noise cannot encompass the impact of successive individual aircraft movements on sleep prevention; but this is only a reiteration of the 'flight numbers issue' which he has separately advanced.

Mr Gordon's submission that the government has itself accepted that Leq is not an acceptable means of measuring night time noise is founded on an exhibit to Miss McWatt's affidavit. It is important to notice that this exhibit was produced in response to a complaint by the applicants that the department had not released any information about night time noise climate. The exhibit is titled: 'Summary of the Background and Reasons surrounding the issue of the publication of Night Time Noise Data by the department.' It is not a pre-existing document, but a text written by Miss McWatt herself in the course of the proceedings to meet a complaint made by the applicant, and, to all intents and purposes, is to be regarded as part of her affidavit. She starts by saying that 'night noise data' are known as 'noise contours'. Then these passages follow:

'The department publishes noise contours for Heathrow, Gatwick and Stansted for the daytime period only ... the department has never published night noise contours to complement the daytime series. The reason is as follows: [there then is some technical discussion (whose merits are not themselves attacked by the applicants)]. The result, in short, is that there is no means of interpreting any night-time contours that might be produced. A particular difficulty would arise in relation to Heathrow where night flights are largely concentrated in two periods up to midnight and after 05.30 ... the use of averaging techniques ... to assess disturbance from aircraft noise is a subject on which there is much academic debate. For that reason [the department] ... has cautioned, for technical reasons, against reliance on Leq contours when there are less than about 30 movements a day. Similar considerations would apply at night.'

In his second affidavit Dr Ollerhead comments on this evidence from Miss McWatt. He says at para 27:

'Miss McWatt referred to the need for caution when interpreting daytime Leq values when the number of events is less than about 30 per day (equivalent to a rate of about 15 per night). She noted that similar considerations might apply at night. Such factors need to be considered very carefully when deciding how best to develop sensible night noise contours, especially when contours could be required for airports with rather different patterns of night operations ... this is not to say that Leq is an inappropriate basis for night noise contours; on the contrary a better alternative seems most unlikely to emerge ...'

I shall assess the impact of this evidence when I come to deal with Mr Gordon's submissions.

I must next recite certain material relevant to what Mr Gordon calls 'the 9 EPNdB issue'. EPNdB is a measure upon which the noise certification data for individual types of aircraft are based, and thus a determinant of any given aircraft type's QC rating. In the consultation paper of January 1993 the department said:

'The noise certification data for each aircraft type has been used as follows: Arrivals: Approach Certification Point Data minus 9 EPNdB (to put on an equivalent basis to departure noise certification points)'

This deduction for landing movements is not further explained in the consultation paper, and is attacked in the applicant's evidence. Dr Ollerhead for the Secretary of State says in his first affidavit at para 20:

'The 9 EPNdB adjustment to the certificated approach noise level in the determination of the QC value for arrivals is made to allow for the fact that, under International Aircraft Noise Certification Procedures, approach noise is measured much nearer to the aircraft than the departure values. Thus, for given certificated noise levels, approach noise footprints are around 10 times larger than departure footprints. The chosen decrement of 9 dB, being the most suitable multiple of the QC class interval (3 dB), simplifies the tabulation of the aircraft data. Such a decrement is, therefore, unremarkable and entirely proper.'

He returns to the theme in his second affidavit, responding to evidence put in by the applicants. He says:

'This differential reflects the fact [that] for a given certificated noise level, take-off noise footprints are typically 10 times bigger than landing footprints. This differential ensures that the footprint area for a given QC value is about the same, regardless of whether the aircraft is landing or taking off. It therefore ensures that like is compared with like.'

Mr Gordon submits that these explanations do not in fact offer any rational basis for the 9 EPNdB deduction. He says, and this is the burden of the assault mounted in his evidence, that it leaves entirely out of account the fact that whereas the main noise impact of take-off is over the airfield, the noise effects of landing are felt at a distance from the airfield; nor does it take on board the fact that at Heathrow some 70% of landings are from the east, an area five times more densely populated than the usual take-off route. So his case is that this deduction has been arrived at leaving wholly out of account the fact that there is a significant number of people who will be more affected by landings than take-offs. He points to the fact, as the evidence shows, that without this deduction the permitted noise levels for landings would be unacceptable on the Secretary of State's own policy (see for example para 30 of the January 1993 consultation paper).

The last issue identified by Mr Gordon is 'the natural justice issue'. In fact there are two points taken here. The first concerns the treatment in the 1993 consultation paper of the provisions in the scheme which are intended to give some flexibility in the event that, in any given season at any given airport, (a) the quota might not be used up, or (b) it might be exceeded. I must set out para 37 of the consultation paper:

'Under the present system at Heathrow, an airport operator is allowed to carry over any unused quota into the following season up to a maximum of 50. It can also bring forward up to 50 from the next season if there is a slight overrun in the current season. (If the overrun exceeds 50, the following season's quota is reduced by double the excess.) This allows a degree of flexibility which has proved useful and which recognises that the summer/winter seasons vary in length from year to year. We propose to allow the three airports to carry over into the next season up to 5 per cent of the quota if there is a surplus or to anticipate up to 5 per cent of the quota of the following season if there is an overrun. If the overrun exceeded 5 per cent, the next season's quota would be reduced by double the excess over 5 per cent. This will continue the flexibility of the existing system without any overall increase in the quota.'

The applicant's complaint is that this passage gave its readers the impression that, for any one season at any one airport, there could be a carry over of up to 5% if there were a surplus, or a carry forward of 5% if there was an overrun, but not both; but it now appears that it was always intended to permit both. The July 1993 press notice says:

'The consultation proposed to allow the airports the facility to carry over 5 per cent of quota if there was a surplus and anticipate up to 5 per cent of the next season's quota in the event of overrun.' (My emphasis.)

Mr Gordon says that in these circumstances his clients have effectively been denied the opportunity of making representations to the effect that this dual flexibility should not be allowed. As a footnote I should state that in fact the press notice proposed 10%, not 5%, flexibility in either direction. That is the result of the consultation process, and is not itself the subject of any complaint before me.

The second natural justice point also depends upon a passage from the consultation paper. It relates to the monitoring of aircraft movements, and hence to the effectiveness of any enforcement of the scheme. It is clear from a letter of 19 August 1993 from the department to a resident living in the locality of Heathrow that: 'Landing aircraft are not monitored against fixed noise limits, but departing aircraft are.' In the consultation paper paras 40 to 43 are in these terms:

'40. The new noise and track monitoring system installed at the three airports ... will monitor the noise made by aircraft to ensure compliance with the maximum noise levels that currently apply for individual departures ...

41. These noise limits have remained unchanged for over 25 years, during which time aircraft have become considerably quieter. As promised earlier, now that the new noise and track monitoring system is operational, it would be appropriate to review the noise limits. We propose to initiate this review and to conduct it through the Aircraft Noise Monitoring Advisory Committee (ANMAC). This committee is chaired by the Department of Transport and comprises representatives of the airlines, airports and local airport consultative committees.

42. We also propose that data from the new Noise and Track Monitoring System should be used to verify the relative noise classification of aircraft types set out in Appendix 2. If over a period of time an aircraft or aircraft type produces noise levels significantly higher or lower than the average for its category, its classification (whether for landing or taking off) would be reconsidered. We propose this should also be overseen by ANMAC.'

Then under the heading 'Penalties':

'43. Instead of the present system of penalties ... BAA [the British Airports Authority] have proposed that if the night-time noise limit is breached at any of the three airports the aircraft owner will incur a financial penalty. It is consulting airlines about this.'

Mr Gordon's complaint is that his clients were reasonably led to believe, by the passage in the consultation paper which I have set out, that landing as well as take-off movements would be monitored, and thus be subject to the facility for enforcement to which monitoring would give rise; and, again, since the true intention was at variance with this (because it contemplated monitoring at take-off only), there has been no proper opportunity to make representations.

I have now described the principal factual material in the case, and turn to the arguments themselves.

The true construction of s 78(3)

Upon this Mr Gordon advanced two submissions. The first was that in exercising the power conferred by the subsection the Secretary of State is obliged to have regard to the existing level of noise and, given the express purpose for which the power is conferred ('avoiding, limiting or mitigating the effect of noise and vibration') he cannot lawfully so exercise it as to produce a result in which noise levels are actually permitted to rise above the levels prevailing at the time at which he acts. Since (a) the use of quieter aircraft has meant that levels have fallen since 1988 but (b) the scheme in contemplation would merely cap levels below those prevailing in 1988, the Secretary of State's proposal travels beyond this limitation of his statutory discretion and would accordingly, if carried into effect, be unlawful.

I reject this argument. It writes into the statute a restrictive provision which has, quite simply, not been enacted. It is of course elementary that the Secretary of State can only use the power for the purpose specified. Mr Gordon's submission, however, depends upon the false logic that this means that the power can never be exercised so as to produce a net increase in noise levels over those prevailing immediately beforehand. In argument I put to him this example: suppose that close to a given airport there exists a large community, many thousands strong, the great majority of whose members work in a particular industry. Desiring to shield them from the effects of aircraft noise, the Secretary of State acts under s 78(3) to impose severe restrictions upon night movements. But with the passage of time the community disperses, because the industry upon which it is dependent falls upon hard times-perhaps closes down altogether. There remain only a village or two, at a greater distance from the airport than the previous conurbation, and with very few inhabitants. The Secretary of State reviews this situation and concludes that the restrictions previously imposed, and still in force, are far more severe than what is now required. He considers that some degree of control under s 78(3) remains necessary for the protection of the villagers. But since they are far fewer in number, and live farther from the airport than was previously the case, their interests do not require anything like so draconian a regime; accordingly, he issues a new notice under s 78(3) whose effect is to permit an increase in the number of night movements, while still maintaining some degree of restriction, and there is a corresponding increase in permitted noise levels.

The example, though of course far distant from the facts of the present case, is useful as illustrating what for my part I take to be obvious, namely that the Secretary of State must look at all the circumstances which he reasonably perceives as relevant at the time he contemplates exercising the power. Given that there is in place an existing regime created under a previous decision, he may conclude that tighter, or looser, restrictions are required; indeed, he may conclude (though it is no doubt improbable in practice, at least in present conditions) that no restrictions are required at all, and in that case he will discharge the previous order. The point is that a decision imposing lighter restrictions than those previously in force may be made to give effect to the statutory purpose just as surely as one which imposes more stringent measures: the content of any decision will depend upon the Secretary of State's perception of what is appropriate in the circumstances.

There is nothing in Mr Gordon's first submission, but his second argument on the construction of s 78(3) has in my judgment much greater force. It may be described in this way. It is clear that the proposed scheme will rely for its legality on s 78(3)(b) (as regards certain aircraft types s 78(3)(a) will also be deployed, but that is irrelevant for present purposes). However, says Mr Gordon, if the Secretary of State implements it, he will be doing something quite outside the words of sub-s (3)(b). He will not 'specify the maximum number of occasions on which aircraft of descriptions so specified may be permitted to take off or land ...' He will specify something entirely different, namely the maximum number of quota points, which, in deciding what movements to schedule, the aircraft operators are not to exceed. He is quite unconcerned with the maximum number of movements. The whole thrust of the scheme, its defining characteristic, is the use of the quota points; they are a mathematical construct which would permit the Secretary of State to impose control by reference to levels of exposure to noise energy, and not by reference to numbers of aircraft movements. But the means of control allowed by s 78(3)(b) is, precisely, numbers of movements; the statute requires that they, and no other concept, are to be the defining characteristic of any order under the sub-paragraph.

Mr Burnett for the Secretary of State sought to lay some emphasis on the express statutory purpose for which the power is conferred, and submitted (correctly) that the scheme is indeed intended to fulfill it. But this cannot help him, since the question on this part of the case is not whether the Secretary of State proposes to act for an alien purpose (which he does not), but whether the means he has chosen to give effect to the subsection's purpose is within the permitted modes of doing so. He submitted that sub-s (3)(b) must be construed in the overall context of the subsection; but this cannot help him either, since he accepts that paras (a), (b) and (c) are exclusive, that is they stipulate the only categories of action allowed to be taken. No appeal to the statutory purpose, or the overall context, can serve to widen any of these categories beyond the limits imposed by their plain words; far less can it vindicate the creation of a fourth category, where indisputably no such category exists.

Mr Burnett's primary argument, however, seeks to come to grips with the language of sub-s (3)(b) in this way: he says that the scheme inexorably dictates a maximum number of movements for each aircraft type, and therefore involves a specification of maximum numbers within the paragraph. In this submission I understood him to be asserting that the form of order when drafted need not set out on its face any actual specification of maxima, so long as the scheme's terms implied a maximum or set of maxima. I greatly doubt whether any scheme would be lawful under sub-s (3)(b) if the maxima in contemplation were not expressed on the face of the document giving effect to it, but Mr Burnett also submits that it would in any event be possible to frame a notice giving effect to the scheme which would set out the maxima explicitly. If that were not possible, I have no doubt then the scheme would certainly be unlawful, because it would not involve the existence of specific maxima capable of being specified expressly, and this, at least, must be a necessary condition for the legality of any scheme under sub-s (3)(b). So I must examine the force of the argument that specific maxima, capable of being expressly specified, are inherent or implied in what the Secretary of State proposes.

Mr Burnett says that the maxima may be expressed in the following table (taking Heathrow as an example):

Description of aircraft Maximum movements

QC 0 5 14,000

QC 1 7,000

QC 2 3,500

QC 4 1,750

I have already said that aircraft with QC 8 and 16 are excluded from night flying at Heathrow. But that is an adventitious fact; if the scheme is lawful, it must also be lawful if such aircraft were included (subject to any separate argument, irrelevant for present purposes and itself extremely doubtful, that any movements by such aircraft could not be permitted at night without contravening Wednesbury principles). But if they were included, Mr Burnett's table would continue as follows:

QC 8 875

QC 16 437 5

Thus logically the scheme involves the possibility that the number of maximum movements could include half a movement. A notice which specified maxima in such terms, whether expressly or by implication, would surely be struck down by the court as specifying something which could only exist in the pages of Lewis Carroll. More concretely, one can see that the maxima on which Mr Burnett is driven to rely are purely notional; they have nothing whatever to do with the real basis on which the Secretary of State proposes to regulate noise at the airports.

Mr Burnett's difficulties, however, do not stop there. The table which I have set out does not, on Mr Burnett's own argument, in fact specify all the maxima which, as he would submit, are implied in the scheme. This is because (for example) the maximum of 14,000 movements at Heathrow for QC 0 5 aircraft applies only if there are no movements by any other aircraft type, and the same is true for each of the other maxima; and any number of movements at QC 0 5 or 1 or 2 or 4 becomes a potential maximum if taken with the number of movements at each of the three other quota levels it produces a result in which all the quota points are exhausted. Thus in order to specify all the maxima implied (or, in Mr Burnett's words, 'inexorably dictated') by the scheme, it would be necessary to set out every possible combination of movements by different aircraft types that might take place so as to use up all the quota points. Yet surely this would be required (I think expressly, but at least by implication) in a notice authorised by s 78(3)(b): Mr Burnett's table as it stands would give the impression that all the maxima specified were jointly permissible; and even if it stated that the four maxima set out were, to use a legalism, not joint but several, it would have failed to specify what the applicable maximum would be for any QC class in the event that the number of movements for any of the other three did not exhaust all the quota points available. The mathematics involved in such an exercise hardly bear contemplation, even I suspect to someone much more numerate than myself. I cannot begin to imagine the length and detail of a notice which expressly specified all the potential maxima implied by the scheme. As sometimes happens with legal arguments, the proof of the pudding is I think in the eating: it is not without interest that the Secretary of State, who is likely to have been contemplating for some time the form of the notice he intends to issue bringing the scheme into effect, has not sought to put a draft before me, at least for illustrative purposes.

I conclude that so far as the scheme may be said to imply the existence of maximum numbers of movements, they are theoretical only; they might (though as it happens they do not) include a maximum not expressed in whole numbers; and they involve such an enormous number of possible combinations of movements among the QC classes that the exercise of expressing them is wholly unreal. And I consider that s 78(5)(c) (which I have set out) could not have any sensible application if the Secretary of State's scheme were brought into effect. The truth is, as Mr Gordon's submission at the outset asserted, that the concept of a maximum number of movements has in practical fact no part to play in the Secretary of State's proposal. Yet under s 78(3)(b) it must be the lynchpin of any order made. It follows, in my judgment, that what is intended is not authorised by the subsection.

I should notice two subsidiary submissions made by Mr Burnett. The first was that if I found (as I have) that the scheme could not fall within sub-s (3)(b) taken on its own, it could be saved by s 78(12). That allows any notice published in pursuance of sub-s (3) to 'contain such incidental or supplementary provisions as the Secretary of State considers appropriate for the purposes of that subsection ...' But if the very basis of the scheme is outwith the primary enabling subsection, it cannot possibly be introduced in the guise of an incidental or supplementary provision.

The second was that if the scheme now proposed is unlawful on the grounds I have described, then so are the existing measures dating from 1988, at least as regards Gatwick. This is because the current arrangements themselves allow a degree of flexibility to aircraft operators which, says Mr Burnett, would fall foul of the same objection as that raised to the present proposals. Logically, of course, this is neither here nor there: if on a particular analysis the present scheme as well as the intended scheme were unlawful, that would of itself be no reason for holding that the analysis is wrong. In fact I do not believe that my conclusions do call into question the validity of the existing regime: I will not go into the detail, since I am not adjudicating upon a challenge to the present arrangements. It is enough to say that they involve the imposition of real, practical, maxima, and such flexibility as exists does not take the regime outside the four corners of the statutory power. There may be a question whether s 78(12) is a necessary ingredient in the present scheme's legality; but I need not go into that.

Given my conclusions on this issue, the application must succeed. Since the scheme has not yet been translated into a notice which would give it effect, I shall hear argument as to the appropriate relief. Although the Secretary of State has undoubtedly made a concrete decision, I doubt whether an order of certiorari going to the press notice of July 1993 is necessary or appropriate; it may be that a declaration will suffice.

My decision on this aspect determines the case, but in case I am wrong, and to pay respect to the arguments I have heard, I should set out my conclusions on Mr Gordon's other points, having already described the principal factual material which bears on them. I will do so as shortly as I can, although the submission which I will deal with next requires some little analysis.

Legitimate expectation and the 1988 policy

The shift of policy (if it was such) of which Mr Gordon complains was on his own case set out in the January 1993 consultation paper. I have set out the relevant extract. The department thus gave fair notice at that time of the aims and limits of the new scheme which it proposed. It follows that Mr Gordon's complaint cannot be of a want of consultation, or a failure to accord a right to be heard. His case is that, notwithstanding the department's announcement of what it proposed, in the very context of a consultation exercise, his clients had a legitimate expectation that the policy would not be shifted so as to procure only a cap of noise levels below those of 1988 (and thus permit, potentially at any rate, an actual increase of noise levels above those prevailing in 1993), irrespective of any opportunity which his clients enjoyed to complain about the proposal between January 1993 and the end of the consultation period.

In large measure Mr Gordon's submissions were designed to persuade me that the law as it has developed will encompass and enforce not only procedural but also substantive legitimate expectations. This is an antithesis which is liable to cause confusion, and it needs to be unravelled in order to expose the barrenness of Mr Gordon's argument.

A public authority may, by an express undertaking or past practice or a combination of the two, have represented to those concerned that it will give them a right to be heard before it makes any change in its policy upon a particular issue which affects them. If so, it will have created a legitimate expectation that it will consult before making changes, and the court will enforce this expectation save where other factors, such as considerations of national security, prevail. This was the position in Council of Civil Service Unions v Minister for the Civil Service [1984] 3 All ER 935, [1985] AC 374. This species of legitimate expectation may be termed 'procedural', because the content of the promise or past practice consists only in the holding out of a right to be heard: a procedural right.

In another case, the public body in question may have adopted a particular policy, and, by promise or past practice, represented that this would be its continuing policy. In this case, there is no promise or past practice to the effect that those affected will be allowed a voice before the policy is changed. But, if (and it will depend on the particular facts) the court concludes that there exists what amounts to an assurance that the policy will continue, it may deem it unfair for the authority to make a change in the policy unless it announces its intention in advance so as to allow an affected person to make representations before any change is carried out. An example of this is R v Secretary of State for the Home Dept, ex p Ruddock [1987] 2 All ER 518, [1987] 1 WLR 1482, where Taylor J, while rejecting the application on its factual merits, accepted in principle that circumstances of this kind might give rise to an enforceable legitimate expectation. He held, what is now commonplace, that the doctrine is rooted in the ideal of fairness. It is important to notice that in holding as he did he was rejecting an argument that the law only recognised the first species of legitimate expectation which I have described, namely that arising where there is a promise or practice of consultation as such (see [1987] 2 All ER 518 at 531, [1987] 1 WLR 1482 at 1494). It is, I think, misleading to describe the type of case exemplified by Ex p Ruddock as one of substantive, in contrast to procedural, expectations, since the case demonstrates no more than that there may be circumstances in which it will be unfair to change a policy adhered to over a period of time without giving those affected a right to be heard: as such the protection afforded is as surely 'procedural' as in the CCSU case. I consider that the putative distinction between procedural and substantive rights in this context has little (if any) utility: the question is always whether the discipline of fairness, imposed by the common law, ought to prevent the public authority respondent from acting as it proposes.

There are other instances in which the courts have upheld legitimate expectations of the type exemplified in Ex p Ruddock. One, much pressed by Mr Gordon, is R v Secretary of State for the Home Dept, ex p Khan [1985] 1 All ER 40, [1984] 1 WLR 1337. But there is no case so far as I am aware (certainly none was cited to me) in which it has been held that there exists an enforceable expectation that a policy will not be changed even though those affected have been consulted about any proposed change. And this is no surprise: such a doctrine would impose an obvious and unacceptable fetter upon the power (and duty) of a responsible public authority to change its policy when it considered that that was required in fulfilment of its public responsibilities. In my judgment the law of legitimate expectation, where it is invoked in situations other than one where the expectation relied on is distinctly one of consultation, only goes so far as to say that there may arise conditions in which, if policy is to be changed, a specific person or class of persons affected must first be notified and given the right to be heard. The extent to which, case by case, this principle applies may be affected by the important distinction between situations where the class of persons in question have specific expectations for the determination of their individual cases (as in Ex p Khan) and others where the policy is of a more general nature which does not involve the resolution of any individual claims of right or status. But it is unnecessary for present purposes to go deeper into such an antithesis.

Mr Gordon relies upon particular words used by Parker LJ in Ex p Khan. He said ([1985] 1 All ER 40 at 46, [1984] 1 WLR 1337 at 1334):

'There can, however, be no doubt that the Secretary of State has a duty to exercise his common law discretion fairly. Furthermore, just as, in the Liverpool Taxi Owners case, the corporation was held not to be entitled to resile from an undertaking and change its policy without giving a fair hearing so, in principle, the Secretary of State, if he undertakes to allow in persons if certain conditions are satisfied, should not in my view be entitled to resile from that undertaking without affording interested persons a hearing and then only if the overriding public interest demands it.'

It is these last words that are stressed by Mr Gordon. He would set them alongside a passage from the judgment of Lord Denning MR in Re Liverpool Taxi Owners' Association [1972] 2 All ER 589 at 594, [1972] 2 QB 299 at 308 where he said:

'At any rate they ought not to depart from it [ie an undertaking] except after the most serious consideration and hearing what the other party has to say; and then only if they are satisfied that the overriding public interest requires it. The public interest may be better served by honouring their undertaking than by breaking it.'

Mr Gordon's submission is that these references to 'the overriding public interest' imply that where a public authority has effectively given an assurance that it would continue to apply a policy which it has adopted, there are two conditions which must be fulfilled before it may lawfully change tack: not only that a right to be heard must be accorded to those affected, but also that the change must be justified by reference to 'the overriding public interest'. But this latter condition would imply that the court is to be the judge of the public interest in such cases, and thus the judge of the merits of the proposed policy change. Thus understood, Mr Gordon's submission must be rejected. The court is not the judge of the merits of the decision-maker's policy. In fact, Mr Gordon disavowed any such proposition; but if (as must be the case) the public authority in question is the judge of the issue whether 'the overriding public interest' justifies a change in policy, then the submission means no more than that a reasonable public authority, having regard only to relevant considerations, will not alter its policy unless it concludes that the public will be better served by the change. But this is no more than to assert that a change in policy, like any discretionary decision by a public authority, must not transgress Wednesbury principles. That, however, is elementary and carries Mr Gordon nowhere.

I was shown an interesting and illuminating article by Dr Christopher Forsyth, 'Provenance and protection of legitimate expectations' [1988] CLJ 238, in which he argues that the doctrine of legitimate expectation may, or should, in some circumstances be deployed so as to protect a substantive expectation of a favourable result in the particular case; and he discusses both Ex p Ruddock and Ex p Khan as well as other material. Dr Forsyth is a distinguished public lawyer to whom I mean no disrespect in saying, without travelling into the detail of his reasoning, that no consideration which he puts forward can, in my judgment, extend the ambit of legitimate expectation to a point which would assist Mr Gordon. I was also shown the recent decisions in R v Board of Inland Revenue, ex p MFK Underwriting Agencies Ltd [1990] 1 All ER 91, [1990] 1 WLR 1545 and R v Jockey Club, ex p RAM Racecourses Ltd [1993] 2 All ER 225; I do not consider that there is anything in either authority inconsistent with the reasoning which I have set out.

It follows that there is nothing in this argument based on legitimate expectation.

Wednesbury and the 1988 policy

Mr Gordon's alternative argument based on para 34 of the 1993 consultation paper is that, if it does not indicate an intended change of policy, then it shows at least that the department misunderstood its own undertaking given in 1988, by confusing the notion of a continuing improvement in noise levels (which was, says Mr Gordon, the substance of the undertaking) with the different notion merely that noise levels should be capped below those prevailing in 1988. For my part I cannot see that there is so concrete a difference between what the department was saying at the two different periods as to give rise to an inevitable inference of inconsistency between them. The 1987 consultation paper which is before me related only to Heathrow; the 1988 press notice was concerned with a five year period, and by its language drew some distinction between Heathrow and Gatwick. In short, the materials on which Mr Gordon relies are not capable of giving rise to a finding of fact (which his submission requires) that in 1993 the Secretary of State had actually misunderstood either his past practice or what had been said on his behalf five years before. So there is nothing in this argument.

The sleep prevention issue

From the passages which I have earlier set out, it is quite clear that the field study report was primarily concerned with problems of aircraft noise and sleep arousal. Had the Secretary of State arrived at his decision in 1993 having literally not considered the possibility that there might be problems relating to sleep prevention, there might be a Wednesbury argument available to Mr Gordon on the basis that an obvious relevant consideration had been ignored. Even this might not be entirely plain sailing, given the passage from Lord Scarman's speech in Findlay v Secretary of State for the Home Dept [1984] 3 All ER 801 at 826-827, [1985] AC 318 at 333-334, where he indorses as correct in English law some observations of Cooke J in CREEDNZ Inc v Governor General [1981] 1 NZLR 172, whose effect as I understand it is that in a case where the statute itself does not specify the considerations to be taken into account in arriving at a discretionary decision, it will be for the decision-making body to decide what is and what is not a relevant consideration, and this decision will itself only be subject to review on Wednesbury grounds. However, it is quite clear on the evidence here that the Secretary of State did have regard to the sleep prevention issue. So much is plain from the Secretary of State's evidence, whose good faith is not in question. There remain the two questions on this part of the case which I set out earlier.

As for the first, it is quite clear that the passage in para 20 of Miss McWatt's affidavit was included to meet a point not now in issue, namely that some legal consequences adverse to the Secretary of State ought to flow from the difference between para 33 of the summary in the final draft, and its substitute, para 34 in the report itself. Had Miss McWatt had in mind, in the passage in question, the wholly different issue for whose purpose her words are now deployed against the Secretary of State, I think it extremely likely that she would have expressed herself differently. However that may be, when one considers Dr Ollerhead's evidence as to the use made of the social survey work and the correlations between the subjective and objective material before the Secretary of State and between the respective rates of complaint of sleep arousal and sleep prevention, I am unable to conclude (by reference to para 20 of Miss McWatt's affidavit) that inherent in the Secretary of State's decision-making process is any critical misunderstanding of the material before him.

As regards the second question on this part of the case which I have identified, I am quite unable to hold that the inference set out by Dr Ollerhead at para 19(c) of his first affidavit gives rise to any Wednesbury complaint. Mr Gordon's argument here (in common, I am bound to say, with much else in his case) is a disguised, though elegant, plea upon the merits. If I were a judge of the merits, I might suppose that Dr Ollerhead's inference as to the extent of any problem relating to sleep prevention is somewhat fragile; but it is manifestly not for me to express any such view, far less treat it as the basis for the grant of relief in judicial review proceedings. It cannot be said that the reasoning under criticism is perverse in the established legal sense. In my judgment this is an area in which any assault on the Secretary of State's decision can only be mounted in an arena outside the court room. I am not suggesting that I would applaud such an assault or deplore it. I say only that the applicant's complaints on this part of the case are not legal complaints, and thus I am in no way concerned with their strengths or weaknesses.

The flight number issue

This is another complaint about the merits dressed in the clothes of a legal issue, and the clothes do not fit. If the Secretary of State chooses, as he has done, to formulate his regulation of aircraft noise control by reference to average noise exposure and without reference (save notionally) to the frequency of flights, that is a matter for him: subject of course, to the point as to the construction of s 78(3)(b), upon which I have separately held in Mr Gordon's favour. In fact the evidence is (in para 16 of Miss McWatt's affidavit) that 'the department does not expect that under the new system there will be any substantial changes or sudden increases in movements at Heathrow at night'.

And she exhibits an extract from Hansard recording the minister's answer to a parliamentary question relating to this aspect. Thus there is no reason to suppose that the Secretary of State was literally blind to any impact which his new policy might in practice have upon flight frequency. The importance he attached to it was wholly a matter for him.

The health effects issue

This argument is misconceived for like reasons. The Secretary of State was not bound by law to obtain specific expert material upon the possibility that aircraft noise might adversely affect the health of a sleeping person, or that of one trying to get to sleep. And Mr Gordon's argument cannot possibly be advanced by the solicitor's affidavit exhibiting the experts' articles to show that health may indeed be affected by noise during sleep. They were not before the Secretary of State.

The Leq issue

Mr Gordon's first submission here, that the government has itself accepted that Leq is an inherently unreliable measure of night time noise, depends in my judgment on a misreading of the exhibit to Miss McWatt's affidavit upon which he relies. The short point is that the conclusion that night time contours, if produced, could not be sensibly interpreted is not the same as, nor does it entail, the proposition that Leq is an unreliable measure of night time noise. As with para 20 of her affidavit, Miss McWatt's exhibit was produced to meet a different complaint from the one upon which Mr Gordon now seeks to rely; the complaint she was meeting, as para 29 of her affidavit demonstrates, was made by Mr Stanbury in paras 30 and 31 of his first affidavit for the applicants and was to the effect that the department had not released any information about the night time noise climate. It is therefore no surprise that the exhibit contains no distinct assertion of the value of Leq as a measure of night time noise. Dr Ollerhead is one of those who are of the view that it is a useful measure, and he refers in para 27 of his second affidavit (I have quoted the passage) to Miss McWatt's exhibit in terms which make it impossible to suppose that he perceived the least inconsistency between what Miss McWatt was saying and his own view of the utility of Leq. I consider that there is no such inconsistency, and there is nothing in this point.

Mr Gordon's further submission under this head, as I have indicated, is that the 3 dB progression used in the quota scheme is not a measure of the increase of noisiness as such but, rather, only of noise energy level. But if in Wednesbury terms the Secretary of State was entitled to take exposure to noise energy levels (and thus Leq) as the touchstone for his proposed regulation (which he was), he cannot be faulted for determining the progression between the energy levels created by different aircraft types by reference to a concept undoubtedly appropriate for the purpose. So this part of Mr Gordon's argument could only succeed if he were able to persuade me that it was an error of law for the Secretary of State to rely on Leq at all, and I have indicated that that is an untenable proposition.

I have already said that Mr Gordon's further submission under this head that Leq should not have been adopted because it cannot measure the impact of successive individual movements is only a reiteration of his argument under the 'flight numbers issue', which I have already rejected.

The 9 EPNdB issue

Mr Gordon complains of the merits of the decision to deduct 9 EPNdB from the approach certification point data on the grounds that it leaves out of account the factual considerations advanced in his clients' evidence and which I have already briefly described. I have also set out Dr Ollerhead's evidence as to why the deduction has been made. I should also notice, as Mr Burnett submitted, that the point having appeared in the consultation paper, there was ample opportunity for representations to be made to the Secretary of State by those who objected to the proposal. In my view this is another area where the complaints advanced raise no point of law. If their effect is that in the result the quota points system is, to say the least, rough and ready because there is no symmetry between the numbers of people affected by the noise of landings and take-offs respectively, or because some people are or may be more affected by landings than by take-offs, those are arguments as to the merits; if I gave effect to them as arguments of law, I would pro tanto be substituting my view as to what a sensible and effective measure under s 78(3) ought to contain for that of the Secretary of State. So I reject Mr Gordon's submission.

The natural justice issues

On the first of these, I propose to say no more than that (despite the use of the disjunctive 'or') I do not consider that para 37 of the January 1993 consultation paper can fairly be read as Mr Gordon suggests. On the second, para 40 in effect indicates that the new system will monitor arrivals; and it sets the context for paras 41 to 43. The paragraphs in question might perhaps have been more clearly expressed. But if (which I do not hold to be the case) there were any doubt of substance as to what the Secretary of State was saying, one would expect respondents to the consultation paper, certainly institutions like the applicants who would rightly wish to scrutinise with great care and vigilance what was being asserted by the department as respects its intended policy, to seek clarification during the consultation period (which ran to 30 April 1993). I do not believe that the applicants are the victims of any want of natural justice.

In the result these applicants must succeed on the single ground as to the construction of s 78(3)(b) upon which I have found in Mr Gordon's favour. That ground could have been determined by reference only to the statute and a description of the intended policy: a few pages of documentation. In fact the material before me on the whole case runs to hundreds of pages. I do not say that all of Mr Gordon's other points were unarguable and ought not to have attracted leave, though I think some of them fall into that category. I do not know whether in giving leave Sedley J, before whom there were oral submissions in court, expressed any view as to the relative merits of any of the grounds. But I think the case illustrates the need, which I regard as pressing, for the provisions of RSC Ord 53 to allow the court to refuse leave on some grounds, while granting it on others, as its view of the application's merits dictates.