ASIA DYEING CO LTD AND OTHERS v. THE AUTHORITY

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J U D G M E N T

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Clough, J.A:

1. This is the judgment of the court.

2. The 27 appellants ("the owners"), who are the owners of chimneys and plant in their premises in the Tsing Yi Industrial Centre on Tsing Yi Island in the New Territories, appeal against the refusal by Barnett J., in proceedings by the owners for judicial review, to set aside notifications given to them under section 9 of the Air pollution Control ordinance (Cap. 311) by the respondent ("the Authority") who is the public officer appointed under section 4 of that Ordinance to be the air pollution control authority in Hong Kong.

3. The notifications were originally given to the owners on the 10th June 1988 requiring them to take anti-pollution measures referred to below. The owners exercised their right under section 31 of the Ordinance to appeal against the requirements of the notifications to the Appeal Board constituted under Part VI of the Ordinance. However on the 9th January 1989, when the appeals were pending, the Authority amended the notifications. Thereafter they have been treated by all concerned as having been given on the date of amendment. On the 1st February 1989 the owners appealed against the requirements of the amended notifications to the Appeal Board under section 31 of the Ordinance. Their appeals have been consolidated. On the 23rd February 1989 their application to the Chairman of the Appeal Board (who has power under section 33(3) of the Ordinance to determine questions of law) to strike out the notifications, as being invalid by reason of failure to comply with the requirements of section 9(1), was dismissed. At the same time the Chairman dismissed the owners application to strike out notices given to the owners by the Authority under section 30 of the Ordinance concurrently with the section 9 notifications.

4. The sequel to the dismissal of their applications by the Chairman of the Appeal Board was a joint application by the owners by way of judicial review to the High Court expressed to be for an order of certiorari to quash the Chairman's decision made on the 23rd February 1989 and "for an Order of Mandamus to set aside" the section 9 and section 30 notices. In the event Barnett J. made an order quashing the Chairman's decision in respect of the section 30 notices and setting them aside. He dismissed the owners' applications in respect of the section 9 notifications which he held to be valid. The owners now appeal against that dismissal.

5. By their notice of appeal the owners seek from this court an order of certiorari to quash the Chairman's decision made on the 23rd February 1989 relating to the section 9 notifications and "an Order of mandamus directing the Air Pollution Control Appeal Board to set aside the section 9 notices". We mention that it seems to us that neither the Chairman nor the Appeal Board (whose powers under section 33(2) of the Ordinance are extended only to confirming, reversing or varying the requirements of a section 9 notification) has the power to set aside a section 9 notification. This seems to have been recognised by the judge below whose order setting aside the section 30 notices was within his powers of judicial review conferred by section 21I(1) of the Supreme Court Ordinance (Cap. 4).

6. The relevant part of the amended section 9 notification given to each of the owners was in the following terms (the words in square brackets having been deleted and the words underlined having been inserted by the amendment made on the 9th January 1989):

"Notice is hereby given to you under Section 9 (1) of the Air pollution Control Ordinance, Cap. 311 (the Ordinance) that your, chimney ......... is in the opinion of the Authority, by the emission of an air pollutant namely sulphur dioxide, contributing to the existence or imminence of an air pollutant nuisance which is prejudicial to health.

[In accordance with section 9(2) (b) of the Ordinance, you are required to eliminate the emission of such pollutant within 90 days from the date of service upon you of this notice.]

You are required by 12th April 1989 to eliminate such emission of sulphur dioxide as exceeds the emission of sulphur dioxide resulting from the combustion of fuel containing 0.5 percent sulphur by weight.

This notice is given to protect health.

....................................................................."

7. The practical effect of the requirement of the notification was that the owners should convert their plant from heavy fuel to light fuel resulting in the emission of less sulphur dioxide. The amendments made to the original notifications are directed to matters connected with the section 30 notices which axe not here relevant.

8. The references in the amended notifications to "the existence or imminence" of a nuisance have given rise to three questions in this appeal because section 9(1) of the Ordinance contemplates that the notifications given by the Authority shall notify the owner of the "existence or imminence, as the case may be," of the relevant nuisance. The three questions are:

(1) Whether the terms of the amended notifications did in any event make it reasonably clear that an existing nuisance was being indicated by the Authority, so that there could be no question of section 9(1) being contravened.

(2) On the footing that question (1) is answered in the negative and that the amended notifications are to be understood to refer to the existence or imminence of the nuisance in the alternative, whether the notifications are nevertheless valid, because section 9(1) is not to be construed as actually requiring the Authority to state in the notification whether in his opinion the nuisance was either existing or imminent, nor is section 9(1) to be construed as precluding a notification in the alternative form.

(3) On the footing that questions (1) and (2) are answered in the negative, whether the relevant requirement of section 9(1) is merely directory or whether it is mandatory so that the amended notifications are vitiated for non-compliance with that requirement.

9. The judge seems to have eased his decision below on his negative answer to question (1). After rehearsing the arguments advanced by counsel for the Authority he concluded the relevant part of his judgment by saying:

"The words complained of do not necessarily add anything, and are therefore not vital to a notice. Thus, if the words are omitted so that a notice simply reads "contributing to an air pollutant nuisance,", there is no doubt in my wind that such a notice would, be valid, being clearly aimed at an existing nuisance. In the present case where the notice is clearly aimed at an existing nuisance, I fail to see how the addition of the words can affect the validity of the notice.

Accordingly, I am satisfied that Mr. Whaley and the Chairman are correct. The notices issued under s.9 are valid. The application in respect of these notices must fail."

10. The relevant provisions of section 9 of the ordinance are as follows:

"9.     (1) On any occasion when, in the opinion of the Authority or of an authorized officer, an air pollutant nuisance exists or is imminent the Authority or such officer shall subject to subsection (5), as soon as practicable after he has become aware thereof, notify, either verbally or in writing, the existence or imminence, as the case may be, of the nuisance to the owner of any premises in which any chimney or relevant plant is, in his opinion, by the emission of any air pollutant, causing or contributing to the existence or imminence of such nuisance.

(2)     Such notification may require the owner forthwith, or at some future time, and for so long as the notification specifies, or until it is withdrawn -

(a) to reduce to such extent as is specified in the notification the emission of the air pollutant from such chimney or relevant plant, as the case may be; or

(b)     in any case where, in the opinion of the Authority or of an authorized officer, such air pollutant nuisance -

(i) is or likely to be prejudicial to healthy; or

(ii) imperils or is likely to imperil the safety of aircraft using or being about to use any airport within Hong Kong, to eliminate the emission of such pollutant.

(3) Where a notification requires the elimination of an emission under subsection (2)(b) it shall contain a declaration that it was given to protect health onto preserve the safety of aircraft, as the case may be."

11. The following definitions contained in section are also relevant:

"air pollutant' means any solid, particulate, liquid, vapour or gaseous substance emitted into the atmosphere;

'air pollutant nuisance' means any emission of air pollutant which either alone or in conjunction with any other such emission-

(a)     is prejudicial to health; or

(b)     is a nuisance to the inhabitants of the neighbourhood; or

(c)     imperils or is likely to imperil the safety of or otherwise interferes with the normal operation of aircraft using or being about to use any airport within Hong Kong;

'prejudicial to health' means injurious, or likely to cause injury, to health;

'relevant plant' means any furnace, engine, oven or industrial plant;"

12. Sections 9 and 10 comprise Part III of the Ordinance under the heading:

"ABATEMENT OF AIR POLLUTION NUISANCES"

13. Section 10 provides:

    "10. (1) Subject to subsection (2), any owner who fails to comply with any of the requirements of a notification given to him under section 9 commits an offence and is liable -

(a)     in any case where such notification contains a declaration that it was given to protect health or to preserve the safety of aircraft, to a fine of $50,000; and

(b)    in any other case, to a fine of $5,000

and in either case to a further fine of $100 in respect of every one quarter of an hour during the whole or any part of which the offence continues.

    (2)A court shall not convict an owner under subsection (1) unless the prosecution proves that the air pollutant nuisance mentioned in the notification existed or was imminent at the time the notification was given to the owner under section 9."

14. Part VI of the Ordinance provides machinery for appeals to the Appeal Board in relation to acts and matters under numerous provisions of the Ordinance. Under section 31(1)(a) and (b) in that Part a person aggrieved by a requirement, of the Authority given under section 9(2)(a) or (b) respectively may appeal to the Board which is empowered under section 33(2) to confirm, reverse or vary the requirement appealed form. Section 31(2) fixes the period for such an appeal at 21 days from the receipt of the notification of the requirement.

15. As regards the effect of a pending appeal upon the operation of a requirement given by the Authority under Section 9(2), section 31(3) provides:

    "(3) Where the ....... requirement appealed from was made under a provision mentioned in paragraphs (a).... of subsection (1) the notice thereof shall be suspended from the day on which notice of appeal is duly given to the Authority and until the appeal is disposed of, withdrawn or abandoned, unless-

    (a) the ......... requirement..... is considered by the Authority to be necessary because the continuation of the activities, whether licensed or otherwise, to which the notice relates would be, or be likely to be, prejudicial to health; and

    (b) the notice contains a declaration to that effect."

16. The absence of any provision for suspension of a requirement imposed under section 9(2)(b) (requiring the elimination of the emission of air pollutant), and appealed against under section 31(1)(b) (as distinct from a "reduction" requirement imposed under section 9 (2) (a) appealed against under section 31(1) (a) and made the subject of a declaration under section 31(3)) is allowed for by section 33(6) in the following terms where the appeal is successful:

    "(6)Where an Appeal Board al lows an appeal under section 31 (1) (a) or (b) it may make an award of -

(a) costs in the case of an appeal under section 31(1)(a), and

(b) costs and compensation in the case of an appeal under section 31 (1) (b),

of such sum, if any, as is just and equitable in ala the circumstances of the case, including the conduct and comparitive (sic) blameworthiness of the appellant and his servants and agents, and of the public officers and any other persons concerned."

17. As regards question (1) (the meaning of the amended notifications), we are unable to accept the interpretation which the judge has put on the notifications. We agree that if, as the judge postulated, the words "the existence or imminence of " had been omitted from the notifications the remaining words "an air pollutant nuisance which is prejudicial to health" would have to be understood as referring to an existing nuisance. However, the problem is caused by the insertion of the words "or imminence" in the notification. The words are there and it will not do to seek to resolve the problem they create by deciding what tie result would have been if they were not there.

18. In our opinion the words "which is prejudicial to health" in the amended notifications must therefore relate, as a matter of interpretation, to the nuisance which is earlier described as being existing or imminent. The quoted words, are, as Mr. Tang rightly contended for the owners, identifying the character of the nuisance which the notifications assert to be existing or imminent.

19. The definition of air pollutant nuisance in section 2 (referring to three types of nuisance) includes

"...any emission of air pollutant which either alone or in conjunction with any other such emission (a) is prejudicial to health".

The effect of the definition in section 2 of "prejudicial to health" is to elaborate that definition to include an emission which is injurious, or likely to cause injury to health. Section 9(1) contemplates inter alia that a nuisance which is of such a character that it is prejudicial to health within the meaning of section 2 may either be actually existing or imminent and that such existence or imminence may be caused or contributed to by the emission from the chimney or relevant plant of, the owner. Accordingly it seems to us that the reference to imminence in the amended notifications cannot, as a matter of interpretation, be rendered meaningless or mere surplusage by the words "which is prejudicial to health".

20. As to question (2) (whether section 9(l) actually requires the Authority to state in the notification whether in his opinion the nuisance is existing or imminent), Mr. Whaley for the Authority contended that whilst section 9 (l) noes appear to envisage that the Authority will specify whether the nuisance, is existing or imminent the provision is not expressed as a procedural requirement or condition and is not therefore a provision to be regarded as intended as a safeguard for the subject. He sought to distinguish and contrast the mandatory terms of section 23(2) of the Town and Country Planning Act 1947 concerning enforcement notices which the House of Lords had to consider (together with section 75 of the Act) in East Riding Count Council v. Park Estate (Bridlington) Ltd [1957] AC 223,(H.L.)

21. We can see no substance in this argument. We accept that there may be circumstances where the legislature manifests by the terms of a statutory provision that it envisages that certain things may be done by an authority but does not require them to be done. However where, as here, section 9(1) expressly provides that the Authority "shall..... notify? the existence or imminence, as the case may be, of the nuisance to the owner...'' it seems to us clear beyond doubt that the legislature is requiring the Authority to notify the existence or imminence of the nuisance to the owner. Likewise in section 9(2)(a) the Authority is required to relate a reduction requirement to a "chimney or relevant plant, as the case may be;" and a requirement under section 9(2) (b) is required by section 9(3) to "contain a declaration that it was given to protect health or to preserve the safety of aircraft, as the case may be.". Moreover, as Lord Hailsham observed in London & Clydeside Estates Ltd. v. Aberdeen D.C. [1980] A.C. 1 W.L.R. 182 (H.L.) at p.189E-F:

    "When parliament lays down a statutory requirement for the exercise of legal authority it expects its authority to be obeyed down to the minutest detail."

22. We therefore conclude that section 9(1) does actually require the Authority to state in the notification whether in his opinion the nuisance is existing or imminent.

23. In our judgment the real issue in this case is that raised by question (3) (whether the relevant requirement in section 9(1) is mandatory or directory) which was the subject of most of the argument on the hearing of the appeal.

24. Where, as in the present case, the legislature has imposed a procedural requirement upon an authority as to the manner in which it is to perform its duty but has not provided what will be the legal consequences of non-compliance the court is left to formulate and apply its own criteria when determining the effect of non-compliance. As Lord Campbell observed in Liverpool Borough Bank v. Turner (1861) 30 L.J.Ch. 379 at p.380:

    "No universal rule can be laid down for the construction of statutes, as to whether mandatory enactment s shall be considered directory only or obligatory, with an implied nullification for disobedience. It is the duty of Courts of justice to try to get at the real intention of the legislature by carefully attending to the whole scope of the statute to be construed."

25. In Howard v. Bodington (1877) 2 P.D. 203 at p.211 Lord Penzance applied that dictum and added:

"I believe, as far as any rule is concerned, you cannot safely go further than that in each case you must look to the subject-matter; consider the importance of the provision that has been disregarded, and the relation of that provision to the general object intended to be secured by the Act and upon a review of the casein that aspect decide whether the matter is what is called imperative or only directory."

26. The above two leading cases are cited in Craies on Statute Law (7th edition) at p.262 and we regard them as providing appropriate guidelines in this case. Mr. Tang helpfully cited passages from Wade on Administrative Law (6th edition) at pp.245 to 250 and passages containing generally similar statements of the relevant principles in de Smith on judicial Review of Administrative Action (4th edition) at pp.142 to 146. We have applied the test laid down in de Smith at p.142 in the following terms:

    "When Parliament prescribes the manner or form in which a duty is to be performed or a power exercised, it seldom lays down what will be the legal consequence's of failure to observe its prescriptions. The courts roust therefore formulate their own criteria for determining whether the procedural rules are to be regarded as mandatory, in which case disobedience wil1 render void or voidable what has been done, or as directory, in which case disobedience will be treated as an irregularity not affecting the validity of what has been done (though in some cases it has been said that there must be substantial compliance with the statutory provisions if the deviation is to be excused as a mere irregularity). Judges have often stressed the impracticability of specifying exact rules for the assignment of a procedural provision to tine appropriate category. The whole scope and purpose of the enactment must be considered, and one must assess the importance of tine provision that has been disregarded, and the relation of that provision to the general object intended to be secured by the Act.' [In assessing the importance of the provision, particular regard may be had to its significance as a protection of individual rights, the relative value that is normally, attached to the rights that may be adversely affected by the decision and the importance of the procedural requirement in the overall administrative scheme established by the statute.] Furthermore, much may depend upon the particular circumstances of the case in hand. Although 'nullification is the natural and usual consequence of disobedience,' breach of procedural or formal rules is likely to be treated as a mere irregularity if the departure from the terms of the Act is of a trivial nature, or if no substantial prejudice has been suffered by those for whose benefit the requirements were introduced, or if serious public inconvenience would be caused by holding them to be mandatory, or if the court is for any reason disinclined to interfere with the act or decision that is impugned."

27. The words in square brackets added by us were not in the same passage in the 3rd edition which was accepted by Templeman J. (as he then was) as providing the appropriate test in Coney v. Choyce [1975] 1 W.L.R. 422. We have read the observations in the above passage on "ubstantial compliance" subject to the dictum of Lord Hailsham in the London and Clydeside Case at pp. 188H to 189C and borne in mind that in that case the failure of the authority which issued the certificate of alternative development to include in the certificate a statement of the relevant rights of appeal of the recipient was held to be a breach of a requirement which was so important as to be mandatory and to render irrelevant the question whether the recipient was actually prejudiced by the authority's breach.

28. We have considered question (3) in the light of the principles referred to above and at the same time borne in mind Mr. Whaley's reminder that section 19 of the interpretation and General Clauses ordinance (Cap. 1) provides that an "Ordinance shall be deemed to be remedial and shall receive such fair, large and liberal construction and interpretation as will best ensure, the attainment of the object of the Ordinance according to its true intent, meaning and spirit".

29. The Air Pollution Control Ordinance is described in its long title as an ordinance "To make provision for abating, prohibiting and controlling pollution of the atmosphere with particular reference to stationary sources and for matters connected therewith". It came into force on the 1st October 1983 and is the successor to the previous Clean Air Ordinance. The general scheme of the ordinance is to deal with different aspects of air pollution under Parts II (air control zones and air quality objectives), III (abatement of air pollution nuisances) and IV (specified processes and the licensing of premises therefor) after providing in Part I (section 4) for the appointment by the Governor of public officer to be the fair pollution control authority (defined in section 2 as the "Authority") for the purposes of carrying out the provisions of the ordinance. The remaining Parts V (enforcement), VI (appeals) and VII (miscellaneous) are of general application.

30. It seems to us that for the purposes of this appeal the court is concerned with the relevant definitions in section 2, Part III which comprises sections 9 and 10, and with relevant provisions in Part VI, namely sections 31, 33 and 36. It is, in our opinion, significant that, although section 9(1) requires the Authority, when he has formed the opinion that an air pollutant nuisance exists or is imminent, to take abatement action which includes notifying the relevant owner of the existence or imminence of the nuisance, no subsequent provision of the ordinance except section 31(3), seems to be actually expressed to provide for any legal or other consequence arising from whether or not the nuisance is stated in the notification to be in existence or only imminent.

31. It is common ground between counsel for both parties to the appeal that the Authority's power conferred by section 9(2) (a) and (b)(i) to require either reduction or elimination of the emission of an air pollutant is exercisable, in the case of an air pollutant nuisance which is or is likely to be prejudicial to health, both where the nuisance is stated in the notification to be in existence and where it is stated to be imminent. It follows that the provisions of section 33(6) relating to costs and compensation in the case of a successful appeal to the Appeal Board do not depend on whether existence or imminence of nuisance is asserted in the notification.

32. The provisions, of section 10 (1) (which are expressed to be subject to section 10(2)) are confined to creating an offence and penalties for failing to comply with any of the requirements off notification. Whereas section 9(1) requires the Authority's notification to notify the existence or imminence of the nuisance, section 10(2) is framed in the reverse order, being expressed to provide that the court may not convict an owner under subsection (1) unless there is proof "that the air pollutant nuisance mentioned in the notification existed or was imminent" at the time the notification was given to the owner under section 9. As it stands, section 10(2), read by itself without reference to section 9(1), seems to provide that in the case of prosecution under section 10 for failure to comply with the requirement of a section 9 notification it is sufficient for the prosecution to prove (1) breach by the owner of the requirement in the notification and (2) that when the notification was given to the owner the nuisance mentioned in the notification either existed or was imminent. Thus either the existence or imminence of the nuisance is expressed to give rise to the duty of the Authority to take action under section 9(1) and is likewise expressed to be required under section 10(2) to be proved in a prosecution under section 10.

33. Appeals under Part VI in relation to section 9 notifications are expressed in section 31 (1) (a) and (b) to be confine to the requirement of the Authority. Although the Chairman of the Appeal Board is given power under section 33(3) to determine a question of law arising before the Board and power under section 36(1) to refer any question of law to the Court of Appeal by way of case stated, such provisions cannot enlarge the jurisdiction of the Board which is confined by section 31 in the manner we have indicated.

34. Section 31(3) seems to include what amounts to an express provision that a reduction requirement imposed under section 9(2)(a) and appealed against under section 31(1)(a) shall not be suspended pending appeal if the notification has indicated the existence of a nuisance which is prejudicial to health. Having regard to the definitions in section 2 of an air pollutant nuisance (which includes any emission of air pollutant which either alone or in conjunction with any other such emission is prejudicial to health in the sense of being injurious or likely to cause injury to health) it seems to us that there is no real difference between, on the one hand an assertion in a notification under section 9(1) that a nuisance which is prejudicial to health exists and, on the other hand, a declaration under section 31(3) in such a notification that the continuation of the activities to which the notification relates would be, or be likely to be prejudicial to health. Put another way, if a section 9 notification identifies an existing nuisance which is expressed to be prejudicial to health it satisfies the requirements of section 31(3) so that if the notification goes on to impose a reduction requirement under section 9(2)(a) any appeal against that requirement would not result in the suspense of the requirement under section 31(3).

35. If, apart from section 31(3), the relevant provisions of the Ordinance are hot expressed to provide for any legal consequence dependent upon whether or not the section 9 notification asserts that the nuisance is either existing or imminent in accordance with the undoubted requirement of section 9(1), is it nevertheless implicit when applying the test laid down in the authorities and the passage, cited from de Smith above that the relevant requirement contained in section 9(1) is so important and essential that non-compliance with that requirement invalidates the notification?

36. The opening words of section 9(1) clearly impose a duty (the relevant word is "shall") on the Authority to give a notification "as soon as practicable" after he has formed the opinion that "an air pollutant nuisance exists or is imminent". In that context the words "as the case may be" do not occur. It seems to us therefore that the broad object of Part III of the Ordinance in relation to public health is to bring about the abatement of any emission of air pollutant which (either alone or in conjunction with any other such emission) actually is or soon will be prejudicial to health (within the definition of that term in section 2). Both situations are within the mischief which the Ordinance is intended to prevent.

37. As a matter of common sense there must from time to time be situations where it is difficult to distinguish, especially on a particular day (see section 10(2)), whether a nuisance is in existence or merely imminent. This, we think, explains why the overall scheme of the relevant provisions in the Ordinance does not (except in the case of section 31(3)) provide for legal consequences flowing from the distinction between the assertion in the section 9(1) notification of either the existence or the imminence of an air pollutant nuisance. It does not make sense to provide that the efficacy of the Authority's measures to protect public health by abating existing or imminent air pollution should depend on whether or not the Authority has accurately assessed by reference to one day (see section 10 (2)) whether or not the nuisance is existing or merely imminent.

38. This court must not indulge in judicial legislation and it must give due weight to the requirement in the second line of section 9(1) that the Authority's notification is to indicate the existence or imminence of the nuisance. In this connection the interpretation of section 10, a penal provision, seems to us to be crucial. Mr. Tang contended, in effect, that the word "shall" in section 9(1) indicated conclusively the mandatory nature of the Authority's obligation to commit himself in the notification to asserting that the nuisance was either existing or imminent. Nothing in section 10 could, Mr. Tang contended, modify the full meaning of hall" in section 9(1), so that the combined effect of sections 9(1) and 10(2) was that section 9(1) must be complied with by the Authority and in a prosecution under section 10 the existence or imminence of the nuisance had to be proved in accordance with what must be asserted in the notification in due compliance with section 9(1).

39. We are unable, after anxious consideration, to accept this argument. We agree that a neat and tidy (but non-purposive and destructive) way to interpret s.10(2) would be to conclude that section 10(2) contemplates only a notification which complies with the letter of section 9(1) and identifies a nuisance which is either existing or imminent, so that if the notification does not do that the prosecution cannot prove its case. It would also follow that if (which we regard as a realistic possibility) the Authority had complied fully with section 9(1) and asserted imminence of the nuisance out the prosecution evidence established an existing nuisance, (or vice versa) the prosecution would fail. In the light of the clear purpose of the legislation this is such a capricious result that we feel constrained to reject the interpretation of section 9 and 10 which produces it, particularly as section 10(2) is actually expressed in terms which do not compel that interpretation.

40. Furthermore the relevant provisions have to be considered, not only by reference to the penal provisions of section 10, but also by reference to the provisions in Part VI relating to appeals. The owners's right of appeal under section 31(1) is confined, in the present circumstances, to an appeal against the requirement contained in a section 9 notification and the Appeal Board has power under section 33(2) to confirm, reverse or vary that requirement.

41. We accept that as Mr. Tang contended, the Authority could well be influenced, in determining the requirement to be imposed on an owner under section 9(2), by whether the Authority asserts that the nuisance is existing or imminent. Thus the time allowed for compliance with the requirement may well be shorter if, an existing nuisance is asserted. In assessing his position on receipt of a section 9 notification and when conducting an appeal against the requirement the owner (and the Appeal Board in the case of an appeal) would therefore have to know whether existence or imminence of the nuisance was alleged.

42. However the effect of the interpretation of sections 9 and 10 advanced by Mr. Tang would seem to be that if, on an appeal against a requirement contained in a section 9 notification which asserted that a nuisance was existing, the Appeal Board determined that the huisance was only imminent, the requirement would have to be reversed and could not be merely varied, because the Authority is obliged by section 9(1) to rely on either existence or imminence but not both. The capriciousness of this result is again emphasised in a case where imminence of the nuisance is alleged in the notification and its actual existence is established on appeal before the Board.

43. We therefore feel constrained to adopt an interpretation of the relevant provisions whim seems to us to be consistent with the underlying intendment of this legislation aria to conclude that the requirement in section 9(l) that the Authority shall identify in the notification the existence or imminence of the nuisance is directory and not mandatory in the sense that non-compliance would vitiate the notification. Likewise we conclude that section 10(2) is to be interpreted as it is actually expressed, so as to indicate that what matters in a prosecution is whether either existence or imminence of the nuisance can be proved.

44. On this basis the recipient of the notification, even if, it is defective in the way in which the present notification is defective for non-compliance with section 9(1), must understand that if he does not comply with the requirement in the notification (subject to the operation of the suspensory provisions of section 31(3) in appropriate circumstances) he can be successfully prosecuted under section 10 if the prosecution is able to prove breach of the requirement and either the existence or the imminence of the nuisance when the notification was given. Similarly, the recipient of, the notification must understand that if he appeals to the Appeal Board against the requirement contained in the notification the Board will have to assess the requirement by reference inter alia to its determination whether the nuisance mentioned in the notification was in existence or imminent or neither existent nor imminent when the notification was given.

45. We have already held that the amended notifications do not in fact identify an existing nuisance. There cannot therefore be any question of the notifications containing a declaration within section 31(3). We add that although the amended notifications use the term "eliminate" they clearly require a reduction of the relevant emission within section 9()(a), so that the owners' appeals come under section 31(1)(a) and the requirements are suspended under section 31(3) pending the disposal of the appeals.

46. Mr. Tang rightly contended that the owner was entitled to know, when he was given a section 9 notification, whether, in accordance with section 9(1), the Authority was asserting the existence or imminence of the relevant nuisance. Clearly the factors which cause or contribute to the imminence of a nuisance way well include factors which are not material to show the actual existence of a nuisance in our opinion the owner is entitled when given a defective notice, as in the present case, to require the Authority to remedy his non-compliance with section 9(1) by informing the owner whether he is asserting that the nuisance in question is existing or imminent. If necessary the owner could obtain an order of mandamus to obtain the required information from the Authority, c.f. the observations of Winn J. (delivering the judgment of the court) in Brayhead (Ascot) Ltd. v. Berkshire County Council [1964] 2 QB 303 (D.C.) at pp.313-4 in relation to non-compliance by a planning authority with a statutory requirement to give written reasons for imposing conditions when issuing a notice granting planning permission.

47. However, for the reasons given above, we do not consider that the defect in the amended notifications is sufficiently important to vitiate the notifications.

48. We therefore uphold the amended notifications in this case despite tine defect arising by reason of the Authority's failure to comply with the requirement under section 9(1) to identify the existence or imminence of the nuisance in question. We apprehend that if formally asked to identify existence or imminence of the nuisance the Authority will reply promptly and say that the nuisance is in fact claimed to exist. This is after all what the Authority has claimed, albeit unsuccessfully in this court, to be what the notifications say. Certainly as long ago as the 1st September 1987 the Authority contended in a standard form letter sent to a number of owners, including 5 of the present appellants that the relevant nuisance then existed. It therefore seems hardly surprising that no request has been made by any of the owners to the Authority to commit itself on the question of the existence or imminence of the nuisance since the original notifications were given on the 10th June 1988.

49. Accordingly we dismiss these appeals and there will be an order nisi awarding the costs of the appeal to the Authority.