unfairly make the insurers liable for the consequences of something which they did not agree to insure.

48. Finally, the FCA asserts that in The B Atlantic [2017] 1 WLR 1303, Christopher Clarke LJ at [26] {J/130/10-11} was “expressly anticipating the disapplication of the but for test in an insurance context where there were concurrent independent causes.”66 This is tenuous at best, for the words quoted by the FCA do not support the assertion, and the case involved interdependent causes (as the passage quoted by the FCA makes clear (“if, as here, both causes need to operate if the loss is to occur”)). In any event, the B Atlantic was appealed to the Supreme Court and no support whatever can be found in the judgment of Lord Mance (with whom the rest of the Court agreed) for any disapplication of the ‘but for’ test where there are concurrent independent causes of loss (see paragraph 54.1 below). Neither Christopher Clarke LJ in the B Atlantic, nor Hamblen J in Orient-Express, nor any other judge in the history of English insurance law, which the parties have no doubt mined to the point of exhaustion, has done so.

49. In all the circumstances, it is fanciful even to suggest that the present is one of those rare and exceptional cases in which the Court could justifiably jettison the ‘but for’ test. This case is not in that territory.

# Concurrent interdependent causes

50. The so-called Wayne Tank principle or Miss Jay Jay rule is not an exception to the application of the ‘but for’ test, because it only applies to concurrent interdependent causes, not to concurrent independent causes.

51. If the loss which is the subject of the claim is caused by concurrent interdependent causes, one of which is covered by the policy and the other is excluded, and the excluded cause is the dominant cause of the loss or a cause of approximately equal

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66 FCA Skeleton at [240] {I/1/96-97}. The specific dictum of Christopher Clarke LJ on which the FCA relies appears to be: “Or it may be that the event would have happened if either A or B had occurred but, on the facts, both of them can be said to have caused it.” It is hardly a ringing endorsement for the FCA’s plunge into unorthodoxy.

efficacy or potency to the cause which is covered, the insured is not entitled to an indemnity under the policy (the exclusion prevails). But if one of the causes is insured, and the other is simply not covered, then the insured is entitled to an indemnity: see the contrasting decisions of the Court of Appeal in Wayne Tank & Pump v Employers’ Liability Assurance [1973] 2 Lloyd’s Rep 237 {K/64} and JJ Lloyd Instruments v Northern Star Insurance Co (The Miss Jay Jay) [1987] 1 Lloyds Rep 32 {J/36}.

52. Both were cases of interdependent concurrent causes of loss: in the former, Lord Denning MR referred to “two causes which were equal or nearly equal in their efficiency” in bringing about the damage67; and in the latter, Lawton LJ indicated that “one [alleged cause] without the other would not have caused the loss…”68

53. The cases are consistent with contract law generally. See, for example, Heskell v Continental Express Ltd (1950) 83 LLR 438 at 458 {K/53/21}, in which Devlin J (as he then was) held that if a breach of contract was one of two separate causes of the loss which were “both co-operating and both of equal efficacy,” that was sufficient to establish liability.

54. The principlesin Wayne Tank and in The Miss Jay Jay and similar cases only apply where there are two causes (i) each of which is a ‘but for’ cause (i.e. without it, the loss would not have occurred), and therefore (ii) both of which combine to bring about the loss. Point (ii) is merely an expression of point (i).69

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67 See [1973] 2 Lloyd’s Rep 237, 240 col 2 {K/64/4}.68 See [1987] 1 Lloyd’s Rep 32, 37 col 2 {J/66/6}.69 In this respect, there is a distinction between cases where there are two or more concurrent causes, whether ‘proximate’ or not, and cases where there is a sole cause, albeit one which may give rise to a number of different legal causes of action or insured perils. That is the perfectly orthodox principle expressed by Potter J in Capel-Cure Myers v McCarthy [1995] LRLR 498 {J/73}, which the FCA cites in its skeleton at [232.2] {I/1/94}. There, the judge said, at 503 {J/73/6} col 1: "... loss by a combination of causes must be distinguished from loss by a single cause, which can nevertheless be properly described as amounting to a number of causes of action, one or more of which may be outside the terms of the policy, but one of which is plainly within its terms.”