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You are here: BAILII >> Databases >> United Kingdom House of Lords Decisions >> Empress Car Company (Abertillery) Ltd [1998] UKHL 5; [1999] 2 AC 22; [1998] 1 All ER 481; [1998] 2 WLR 350 (5th February, 1998)
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Cite as: [1998] UKHL 5, [1999] 2 AC 22, [1998] 1 All ER 481, [1998] 2 WLR 350

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Empress Car Company (Abertillery) Ltd [1998] UKHL 5; [1999] 2 AC 22; [1998] 1 All ER 481; [1998] 2 WLR 350 (5th February, 1998)

HOUSE OF LORDS

Lord Browne-Wilkinson Lord Lloyd of Berwick Lord Nolan
Lord Hoffmann Lord Clyde

OPINIONS OF THE LORDS OF APPEAL FOR JUDGMENT IN THE CAUSE

EMPRESS CAR COMPANY (ABERTILLERY) LTD.
(APPELLANTS)

v.

NATIONAL RIVERS AUTHORITY
(RESPONDENTS)

ON 5 FEBRUARY 1998

LORD BROWNE-WILKINSON

My Lords,

I have had the advantage of reading in draft the speech prepared by my noble and learned friend, Lord Hoffmann. For the reasons he gives I would dismiss the appeal.

LORD LLOYD OF BERWICK

My Lords,

I have had the advantage of reading in draft the speech prepared by my noble and learned friend, Lord Hoffmann. For the reasons he gives I too would dismiss this appeal.

LORD NOLAN

My Lords,

I have had the advantage of reading a draft of the speech of my noble and learned friend Lord Hoffmann. For the reasons he has given, I too would dismiss this appeal.

LORD HOFFMANN

My Lords,

Empress Car Company (Abertillery) Ltd. ("the company") was convicted at the Crown Court sitting at Newport, Gwent (His Honour Judge Crowther Q.C. and two justices) of "causing poisonous, noxious or polluting matter or sold waste to enter controlled waters" contrary to section 85(1) of the Water Resources Act 1991. "Controlled waters" are defined in section 104(1)(c) and (3) to include any river and in this case were the waters of the River Ebbw Fach, which ran close by the company's premises in Abertillery. A large quantity of diesel oil had escaped from a tank into the river in circumstances which I shall shortly describe. Section 85(1) reads as follows:

The company was originally convicted by the Tredegar justices and appealed to the Crown Court. Its appeal from the Crown Court to the Divisional Court by way of case stated was also dismissed. It now appeals to your Lordships' House. The facts as found in the case stated may be summarised as follows. The company maintained a diesel tank in a yard which was drained directly into the river. The tank was surrounded by a bund to contain spillage, but the company had overridden this protection by fixing an extension pipe to the outlet of the tank so as to connect it to a drum standing outside the bund. It appears to have been more convenient to draw oil from the drum than directly from the tank. The outlet from the tank was governed by a tap which had no lock. On 20 March 1995 the tap was opened by a person unknown and the entire contents of the tank ran into the drum, overflowed into the yard and passed down the drain into the river.

The Crown Court found that there was a history of local opposition to the company's business. The tap might have been turned on by a malicious intruder, an aggrieved visitor or an upset local person. The incident coincided with a public inquiry about a disputed footpath which was to be held on the following day. But the court made no finding as to the identity of the person who turned on the tap. The evidence was consistent with it having been an employee or a stranger. The court held that it did not matter because on either view the company had "caused" the oil to enter the river. In the case stated, the court gave the following reasons:

The company's case before the Divisional Court was that if the evidence was consistent with the tap having been opened by a stranger, it should have been acquitted. The escape would have been caused by the stranger and not the company. The Divisional Court disagreed, saying that although it would be true to say that the escape had been caused by the stranger, it was open to the Crown Court to find that it had also been caused by the company. But they said that the authorities on the subject were not easy to reconcile and certified the following question of general public importance:

section 85

Water Resources Act 1991

(a) he held the polluting matter and contained it in such a way as it would not escape but for a positive act by himself or another; and

Before your Lordships, Mr. Philpott for the company repeated his submission that the cause of the escape was not the keeping of the oil by the company but the opening of the tap by the stranger. He also said that "causing" for the purposes of section 85(1) required some positive act and that the escape could not be said to have been caused by any such act by the company. All it had done was to create a state of affairs in which someone else could cause the oil to escape. There are accordingly two issues in the case. The first is whether there has to have been some "positive act" by the company and, if so, whether the company did such an act. The second is whether what it did "caused" the oil to enter the river.

1. Acts and omissions

My Lords, the two limbs of section 2(1)(a) of the Rivers (Prevention of Pollution) Act 1951, which was in the same terms as section 85(1) of the 1991 Act, were analysed by Lord Wilberforce in Alphacell Ltd. v. Woodward [1972] AC 824, 834:

causing

knowingly permitting

Putting the matter shortly, if the charge is "causing", the prosecution must prove that the pollution was caused by something which the defendant did, rather than merely failed to prevent. It is, however, very important to notice that this requirement is not because of anything inherent in the notion of "causing". It is because of the structure of the subsection which imposes liability under two separate heads: the first limb simply for doing something which causes the pollution and the second for knowingly failing to prevent the pollution. The notion of causing is present in both limbs: under the first limb, what the defendant did must have caused the pollution and under the second limb, his omission must have caused it. The distinction in section 85(1) between acts and omissions is entirely due to the fact that Parliament has added the requirement of knowledge when the cause of the pollution is an omission. Liability under the first limb, without proof of knowledge, therefore requires that the defendant must have done something.

In this sense, Mr. Philpott is right in saying that there must have been some "positive act" by the company. But what counts as a positive act? We were referred to two cases in which the defendant's conduct had been held to be insufficient. In Price v. Cromack [1975] 1 W.L.R. 988 the defendant maintained two lagoons on his land into which, pursuant to an agreement, the owners of adjoining land discharged effluent. The lagoons developed leaks which allowed the effluent to escape into the river. Lord Widgery C.J. said that the escape had not been caused by anything which the defendant had done. There was no "positive act" on his part. The effluent came onto the land by gravity and found its way into the stream by gravity "with no act on his part whatever:" see p. 994. The other case is Wychavon District Council v. National Rivers Authority [1993] 1 W.L.R. 125. The council maintained the sewage system in its district as agent for the statutory authority, the Severn Trent Water Authority. It operated, maintained and repaired the sewers. As sewage authority, it received raw sewage into its sewers. On the occasion in question one of the sewers became blocked. The sewage flowed into the stormwater drainage system and into the River Avon. The Divisional Court held that the Council had not done any positive act which caused the pollution. If it had known of the blockage it might have been liable for "knowingly permitting" but it could not be liable for causing.

My Lords, in my opinion these two cases take far too restrictive a view of the requirement that the defendant must have done something. They seem to require that his positive act should have been in some sense the immediate cause of the escape. But the Act contains no such requirement. It only requires a finding that something which the defendant did caused the pollution. I shall come later to the question of what amounts to causing. Assuming, for the moment, that there was a sufficient causal connection between the maintaining of the lagoons in Price v. Cromack or the operation of the sewage system in Wychavon District Council v. National Rivers Authority and the respective escapes, I do not see why the justices were not entitled to say that the pollution was caused by something which the defendants did. Maintaining lagoons of effluent or operating the municipal sewage system is doing something.

In National Rivers Authority v. Yorkshire Water Services Ltd. [1995] 1 A.C. 444 the House was invited to say that the law had "taken a wrong turning" in the requirement of a "positive act" as formulated in Price v. Cromack and Wychavon District Council v. National Rivers Authority. Lord Mackay of Clashfern L.C., at p. 452, said that he regarded those cases as turning on their own facts but added that the word "cause" should be used in its ordinary sense and that "it is not right as a matter of law to add further requirements." In Attorney-General's Reference (No. 1 of 1994) [1995] 1 W.L.R. 599, 615 Lord Taylor of Gosforth C.J. in the Court of Appeal said, in my view rightly, that the insistence in Price v. Cromack and Wychavon District Council v. National Rivers Authority on a positive act as the immediate cause of the escape was a "further requirement" which should not have been added. The only question was whether something which the defendant had done, whether immediately or antecedently, had caused the pollution.

In the present case, the Crown Court found that the escape was caused by the way the company maintained its tank of diesel fuel. Maintaining a tank of diesel is doing something and therefore, provided that it was open to the court to find the necessary causal connection established, they were in my view entitled to convict. It is to the notion of causing that I therefore now turn.

2. Causing

The courts have repeatedly said that the notion of "causing" is one of common sense. So in Alphacell Ltd. v. Woodward [1972] AC 824, 847 Lord Salmon said:

I doubt whether the use of abstract metaphysical theory has ever had much serious support and I certainly agree that the notion of causation should not be overcomplicated. Neither, however, should it be oversimplified. In the Alphacell case, at p. 834, Lord Wilberforce said in similar vein:

The last concession was prudently made, because it is of course the causal significance of acts of third parties (as in this case) or natural forces that gives rise to almost all the problems about the notion of "causing" and drives judges to take refuge in metaphor or Latin. I therefore propose to concentrate upon the way common sense notions of causation treat the intervention of third parties or natural forces. The principles involved are not complicated or difficult to understand, but they do in my opinion call for some explanation. It is remarkable how many cases there are under this Act in which justices have attempted to apply common sense and found themselves reversed by the Divisional Court for error of law. More guidance is, I think, necessary.

The first point to emphasise is that common sense answers to questions of causation will differ according to the purpose for which the question is asked. Questions of causation often arise for the purpose of attributing responsibility to someone, for example, so as to blame him for something which has happened or to make him guilty of an offence or liable in damages. In such cases, the answer will depend upon the rule by which responsibility is being attributed. Take, for example, the case of the man who forgets to take the radio out of his car and during the night someone breaks the quarterlight, enters the car and steals it. What caused the damage? If the thief is on trial, so that the question is whether he is criminally responsible, then obviously the answer is that he caused the damage. It is no answer for him to say that it was caused by the owner carelessly leaving the radio inside. On the other hand, the owner's wife, irritated at the third such occurrence in a year, might well say that it was his fault. In the context of an inquiry into the owner's blameworthiness under a non-legal, common sense duty to take reasonable care of one's own possessions, one would say that his carelessness caused the loss of the radio.

Not only may there be different answers to questions about causation when attributing responsibility to different people under different rules (in the above example, criminal responsibility of the thief, common sense responsibility of the owner) but there may be different answers when attributing responsibility to different people under the same rule. In National Rivers Authority v. Yorkshire Water Services Ltd. [1995] 1 A.C. 444 the defendant was a sewerage undertaker. It received sewage, treated it in filter beds and discharged the treated liquid into the river. One night someone unlawfully discharged a solvent called iso-octanol into the sewer. It passed through the sewage works and entered the river. The question was whether the defendant had caused the consequent pollution. Lord Mackay of Clashfern L.C., with whom the other members of the House agreed, said, at p. 452:

So in the context of attributing responsibility to Yorkshire Water Services under section 85(1) (then section 107(1)(a) of the Water Act 1989), it had caused the pollution. On the other hand, if the person who put the iso-octanol into the sewer had been prosecuted under the same subsection, it would undoubtedly have been held that he caused the pollution.

What these examples show is that it is wrong and distracting, in the case of a prosecution under section 85(1), to ask "What caused the pollution?". There may be a number of correct answers to a question put in those terms. The only question which has to be asked for the purposes of section 85(1) is "Did the defendant cause the pollution?" The fact that for different purposes or even for the same purpose one could also say that someone or something else caused the pollution is not inconsistent with the defendant having caused it. The way Lord Wilberforce put it in Alphacell Ltd. v. Woodward [1972] AC 824, 835 was as follows:

I turn next to the question of third parties and natural forces. In answering questions of causation for the purposes of holding someone responsible, both the law and common sense normally attach great significance to deliberate human acts and extraordinary natural events. A factory owner carelessly leaves a drum containing highly inflammable vapour in a place where it could easily be accidentally ignited. If a workman, thinking it is only an empty drum, throws in a cigarette butt and causes and explosion, one would have no difficulty in saying that the negligence of the owner caused the explosion. On the other hand, if the workman, knowing exactly what the drum contains, lights a match and ignites it, one would have equally little difficulty in saying that he had caused the explosion and that the carelessness of the owner had merely provided him with an occasion for what he did. One would probably say the same if the drum was struck by lightning. In both cases one would say that although the vapour-filled drum was a necessary condition for the explosion to happen, it was not caused by the owner's negligence. One might add by way of further explanation that the presence of an arsonist workman or lightning happening to strike at that time and place was a coincidence.

On the other hand, there are cases in which the duty imposed by the rule is to take precautions to prevent loss being caused by third parties or natural events. One example has already been given; the common sense rule (not legally enforceable, but neglect of which may expose one to blame from one's wife) which requires one to remove the car radio at night. A legal example is the well-known case of Stansbie v. Troman [1948] 2 K.B. 48. A decorator working alone in a house went out to buy wallpaper and left the front door unlocked. He was held liable for the loss caused by a thief who entered while he was away. For the purpose of attributing liability to the thief (e.g. in a prosecution for theft) the loss was caused by his deliberate act and no one would have said that it was caused by the door being left open. But for the purpose of attributing liability to the decorator, the loss was caused by his negligence because his duty was to take reasonable care to guard against thieves entering.

These examples show that one cannot give a common sense answer to a question of causation for the purpose of attributing responsibility under some rule without knowing the purpose and scope of the rule. Does the rule impose a duty which requires one to guard against, or makes one responsible for, the deliberate acts of third persons? If so, it will be correct to say, when loss is caused by the act of such a third person, that it was caused by the breach of duty. In Stansbie v. Troman [1948] 2 K.B. 48, 51-52, Tucker L.J. referred to a statement of Lord Sumner in Weld-Blundell v. Stephens [1920] A.C. 956, 986, in which he had said:

Tucker L.J. went on to comment:

Before answering questions about causation, it is therefore first necessary to identify the scope of the relevant rule. This is not a question of common sense fact; it is a question of law. In Stansbie v. Troman the law imposed a duty which included having to take precautions against burglars. Therefore breach of that duty caused the loss of the property stolen. In the example of the vapour-filled drum, the duty does not extend to taking precautions against arsonists. In other contexts there might be such a duty (compare The Fiona [1994] 2 Lloyd's Rep. 506, 522) but the law of negligence would not impose one.

What, therefore, is the nature of the duty imposed by section 85(1)? Does it include responsibility for acts of third parties or natural events and, if so, for any such acts or only some of them? This is a question of statutory construction, having regard to the policy of the Act. It is immediately clear that the liability imposed by the subsection is strict: it does not require mens rea in the sense of intention or negligence. Strict liability is imposed in the interests of protecting controlled waters from pollution. The offence is, as Lord Pearson said in Alphacell Ltd. v. Woodward [1972] AC 824, 842, "in the nature of a public nuisance." National Rivers Authority v. Yorkshire Water Services Ltd. [1995] 1 A.C. 444 is a striking example of a case in which, in the context of a rule which did not apply strict liability, it would have been said that the defendant's operation of the sewage plant did not cause the pollution but merely provided the occasion for pollution to be caused by the third party who discharged the iso-octanol. And in Alphacell Ltd. v. Woodward [1972] AC 824, 835, Lord Wilberforce said with reference to Impress (Worcester) Ltd. v. Rees [1971] 2 All E.R. 357, which I shall discuss later, that:

Clearly, therefore, the fact that a deliberate act of a third party caused the pollution does not in itself mean that the defendant's creation of a situation in which the third party could so act did not also cause the pollution for the purposes of section 85(1).

It is not easy to reconcile this proposition with the actual decision of the Divisional Court in Impress (Worcester) Ltd. v. Rees [1971] 2 All E.R. 357, to which I have just referred. The appellants kept a fuel oil storage tank with an unlocked valve in their yard near the river. An unauthorised person entered during the night and opened the valve. The justices convicted but the Divisional Court allowed the appeal. Cooke J. said:

That question, said the Divisional Court, was capable of only one answer, namely that "it was not the conduct of the appellants but the intervening act of the unauthorised person which caused the oil to enter the river." In Alphacell Ltd. v. Woodward [1972] AC 824, 835, Lord Wilberforce said that he did not "desire to question this conclusion" and Lord Salmon said that it was an example of "the active intervention of a stranger, the risk of which could not reasonably have been foreseen." The difficulty is, however, that the justices said nothing about whether the risk could reasonably have been foreseen and nor did the Divisional Court. The nearest which the justices came to this question was when they said "the valve was never locked but . . . the appellants ought to have kept it closed at all material times"--a remark which rather suggests that the possibility of tampering should have been foreseen. Whether foreseeability was a relevant matter at all is a point to which I shall return later. But the actual reasoning of the Divisional Court was that the defendant was entitled to be acquitted simply because the escape had been caused by the deliberate act of a stranger. Mr. Philpott urged upon us that the reasoning in Impress (Worcester) Ltd. v. Rees applied squarely to this case and I think that he is right. But in my view the case was wrongly decided. It is inconsistent with Lord Wilberforce's statement that the deliberate act of a third party does not necessarily negative causal connection and with the subsequent decision of this House in National Rivers Authority v. Yorkshire Water Services Ltd. [1995] 1 A.C. 444.

While liability under section 85(1) is strict and therefore includes liability for certain deliberate acts of third parties and (by parity of reasoning) natural events, it is not an absolute liability in the sense that all that has to be shown is that the polluting matter escaped from the defendant's land, irrespective of how this happened. It must still be possible to say that the defendant caused the pollution. Take, for example, the lagoons of effluent in Price v. Cromack [1975] 1 W.L.R. 988. They leaked effluent into the river and I have said that in my view the justices were entitled to hold that the pollution had been caused by the defendant maintaining leaky lagoons. But suppose that they emptied into the river because a wall had been breached by a bomb planted by terrorists. I think it would be very difficult to say, as a matter of common sense, that the defendant had caused the pollution. On what principle, therefore, will some acts of third parties (or natural events) negative causal connection for the purposes of section 85(1) and others not?

In Alphacell Ltd. v. Woodward [1972] AC 824 Lord Salmon, as I have mentioned, suggested that the difference might depend upon whether the act of a third party or natural event was foreseeable or not. This was the approach taken by the justices in National Rivers Authority v. Wright Engineering Co. Ltd. [1994] 4 All E.R. 281. That was another case of vandalism leading to oil escaping from a tank into a river. The justices acquitted because they said that although there had been past incidents of vandalism at the defendant's premises, "the vandalism involved was not reasonably foreseeable because it was out of all proportion to the earlier and more minor incidents." In the Divisional Court, Buckley J., at p. 285, cited with approval a remark of Lloyd L.J. in the Divisional Court in Welsh Water Authority v. Williams Motors (Cwmdu) Ltd. The Times, 5 December 1988:

Nevertheless, said Buckley J.:

I have already said that I think that to frame the question as "who or what caused the result under consideration" is wrong and distracting, because it may have more than one right answer. The question is whether the defendant caused the pollution. How is foreseeability a relevant factor to consider in answering this question?

In the sense in which the concept of foreseeability is normally used, namely as a ingredient in the tort of negligence, in the form of the question: ought the defendant reasonably to have foreseen what happened, I do not think that it is relevant. Liability under section 85(1) is not based on negligence; it is strict. No one asked whether Yorkshire Water Services Ltd ought to have foreseen that someone would put iso-octanol in their sewage. Likewise in C.P.C. (U.K.) Ltd. v. National Rivers Authority [1994] Env. L.R. 131 the defendant operated a factory which used cleaning liquid carried through PVC piping. The piping leaked because it had been badly installed by the reputable subcontractors employed by the previous owners of the factory. The Court of Appeal held that although the defendants were unaware of the existence of the defect and "could not be criticised for failing to discover it," the pollution had nevertheless been caused by their operation of the factory. So the fact that the negligent installation of the pipes had been unforeseeable was no defence. I agree with Lloyd L.J. that the question is not whether the consequences ought to have been foreseen; it is whether the defendant caused the pollution. And foreseeability is not the criterion for deciding whether a person caused something or not. People often cause things which they could not have foreseen.

The true common sense distinction is, in my view, between acts and events which, although not necessarily foreseeable in the particular case, are in the generality a normal and familiar fact of life, and acts or events which are abnormal and extraordinary. Of course an act or event which is in general terms a normal fact of life may also have been foreseeable in the circumstances of the particular case, but the latter is not necessary for the purposes of liability. There is nothing extraordinary or abnormal about leaky pipes or lagoons as such: these things happen, even if the particular defendant could not reasonably have foreseen that it would happen to him. There is nothing unusual about people putting unlawful substances into the sewage system and the same, regrettably, is true about ordinary vandalism. So when these things happen, one does not say: that was an extraordinary coincidence, which negatived the causal connection between the original act of accumulating the polluting substance and its escape. In the context of section 85(1), the defendant's accumulation has still caused the pollution. On the other hand, the example I gave of the terrorist attack would be something so unusual that one would not regard the defendant's conduct as having caused the escape at all.

In the context of natural events, this distinction between normal and extraordinary events emerges in the decision of this House in Alphacell Ltd. v. Woodward [1972] AC 824. The defendant operated a paper manufacturing plant which involved maintaining tanks of polluting liquid near the river, so that pollution would occur if they overflowed. There were pumps which ought normally to have drawn off the liquid and prevented the tanks from overflowing. But in late November the pumps became choked with brambles, ferns and long leaves: they did not function and an overflow occurred. The House found no difficulty in holding that the pollution was caused by what the defendant had done: Lord Wilberforce said that "the whole complex operation which might lead to this result was an operation deliberately conducted by the appellants . . . ." As for "causing," it was true that the pollution would not have happened but for a natural event, namely, the vegetation getting into the pumps, but, as Lord Pearson said, at p. 845, that was nothing extraordinary:

Lord Salmon said it would have been different if there had been an "Act of God", which I take to mean some extraordinary natural event. Likewise in the case of the acts of third parties, I think that once one accepts, as in the light of Lord Wilberforce's comments in Alphacell and the decision in National Rivers Authority v. Yorkshire Water Services Ltd. [1995] 1 A.C. 444 one has to accept, that some deliberate acts of third parties will not negative causal connection, it seems to me that the distinction between ordinary and extraordinary is the only common sense criterion by which one can distinguish those acts which will negative causal connection from those which will not.

So I think that the defendant in Impress (Worcester) Ltd. v. Rees was rightly convicted by the justices and that the defendant in National Rivers Authority v. Wright Engineering Co. Ltd. [1994] 4 All E.R. 281 should also have been convicted. The particular form of vandalism may not have been foreseeable (someone had broken the sight gauge) but the precise details will never be foreseeable. In practical terms it was ordinary vandalism.

I shall try to summarise the effect of this discussion.

(1) Justices dealing with prosecutions for "causing" pollution under section 85(1) should first require the prosecution to identify what it says the defendant did to cause the pollution. If the defendant cannot be said to have done anything at all, the prosecution must fail: the defendant may have "knowingly permitted" pollution but cannot have caused it.

(2) The prosecution need not prove that the defendant did something which was the immediate cause of the pollution: maintaining tanks, lagoons or sewage systems full of noxious liquid is doing something, even if the immediate cause of the pollution was lack of maintenance, a natural event or the act of a third party.

(3) When the prosecution has identified something which the defendant did, the justices must decide whether it caused the pollution. They should not be diverted by questions like "What was the cause of the pollution?" or "Did something else cause the pollution?" because to say that something else caused the pollution (like brambles clogging the pumps or vandalism by third parties) is not inconsistent with the defendant having caused it as well.

(4) If the defendant did something which produced a situation in which the polluting matter could escape but a necessary condition of the actual escape which happened was also the act of a third party or a natural event, the justices should consider whether that act or event should be regarded as a normal fact of life or something extraordinary. If it was in the general run of things a matter of ordinary occurrence, it will not negative the causal effect of the defendant's acts, even if it was not foreseeable that it would happen to that particular defendant or take that particular form. If it can be regarded as something extraordinary, it will be open to the justices to hold that the defendant did not cause the pollution.

(5) The distinction between ordinary and extraordinary is one of fact and degree to which the justices must apply their common sense and knowledge of what happens in the area.

Applying these principles, it seems to me that there was ample evidence on which the Crown Court was entitled to find that the company had caused the pollution. I would therefore dismiss the appeal.

LORD CLYDE

My Lords,

The appellant was convicted on a complaint that on 20 March 1995 he "did cause polluting matter, namely diesel oil, to enter controlled waters, namely the River Ebbw Fach . . . contrary to section 85(1) of the Water Resources Act 1991." The oil had escaped from a tank on the appellant's premises, flowed onto a yard within the premises, into a storm drain which served to drain the yard, and thereby into the river. It was evident that the oil had left the tank through an outlet which was governed by a tap. The tap had been turned on. It was not proved who had turned it on. It could, and probably was a member of the appellant's staff, but it could have been an intruder. There was no doubt that the oil was polluting matter and no doubt that it had entered the controlled waters. The question for the Justices and for the Crown Court on appeal was whether the prosecution had proved that the appellant had caused the oil to enter the waters.

A contravention of section 85(1) occurs where a person "causes or knowingly permits" a pollutant to enter controlled waters. The context gives some guidance towards the identification of what is meant by "cause." It must involve some kind of active operation by the defendant whereby, with or without the occurrence of other factors, the pollutant enters the controlled waters. If the defendant has simply stood back and not participated to any extent at all, although he might have been guilty of knowingly permitting it, but he will not have caused the pollutant to enter the waters. It is sufficient that his activity has been a cause; it does not require to be the cause. Moreover it is not necessary for the prosecution to prove knowledge, foreseeability, negligence nor intention. These matters may or may not be identified as elements in the history but they are not essentials for the proof of the offence. Furthermore, in determining whether the prosecution has proved that the defendant caused the pollutant to enter the waters account has to be taken of natural forces, acts of God and the actions of third parties, if the evidence justifies taking such considerations into account either as contributing causes or even as excluding any operation of the defendant as a causative factor. The action of a third party may in some cases be merely one of the concurrent causes. Alternatively it may in other cases be so far out of the ordinary course of things that in the circumstances any active operations of the defendant fade into the background.

There may be a danger in enlarging on any definition of what may constitute a cause that particular expressions may become elevated into standard tests which may distract attention from the critical question which the statute requires to be addressed or invite concentration on an issue whose formulation may not quite meet the statutory terms. The use of alternative language to that used by the statute may only lead to debate about the precise meaning of such alternative expressions and obscure the true question. The use of the expression "positive act," which appears in the certified question in the present appeal, seems to me to be open to that objection. As the Lord Chancellor, Lord Mackay of Clashfern, observed in N.R.A. v. Yorkshire Water Services Ltd. [1995] A.C. 444, 452 "the word 'cause' is to be used in its ordinary sense in these provisions and it is not right as matter of law to add further requirements." While I have adopted the language used by Lord Wilberforce in Alphacell Ltd. v. Woodward [1972] AC 824, of "active operation" I do not consider that it is to be regarded as anything more than a reminder that in the present context absolute passivity is not enough to constitute a cause. The maintaining of a system, the carrying on of an enterprise, and the management of a going concern may each constitute causative factors. So also may the discontinuing of an enterprise or the closing down of a concern, as in the case of Lockhart v. National Coal Board, 1981 S.L.T. 161. In many cases an omission may be analysed as the provision or operation of an inadequate or deficient system. Thus a failure to take precautions in relation to a risk of the escape of a pollutant in the course of the management of premises such as those which the appellants were occupying in the present case may be seen as an active operation for the purposes of causation.

I would also wish to avoid the language of foreseeability in relation to the inquiry into causation. In deciding whether some particular factor has played so important a part that any activity by the defendant should be seen as entirely superseded as a causative element it is not a consideration of the foreseeability, or reasonable foreseeability, of the extraneous factor which seems to me to be appropriate, but rather its unnatural, extraordinary or unusual character. Matters of fault or negligence are not of immediate relevance in the present context and the concepts particularly related to those matters should best be avoided.

The question in the present case is not whether the appellant caused the oil to leave the tank but the larger question whether the appellant caused the oil to enter the controlled waters. In light of the facts it was in my view certainly open to the Justices and the Crown Court to conclude that the appellant had caused the oil to enter the controlled waters. I have regard in particular to the provision of an exposed and unguarded tap in a situation where the premises were not secure against invasion, where on account of the local opposition to the appellant's business the malicious or thoughtless intervention of a third party would not be something out of the ordinary course, and where in the event of any escape of oil out of the tap onto the ground the layout was such as to carry such oil to the yard, to the storm drain and so to the river.

The decisions in the various cases to which we were referred, must in my view be seen as depending upon the particular facts of each of them. So far as the present case is concerned, I would dismiss the appeal.