Per Lindley LJ in Reischer v Borwick  2 QB 548 at p.550:
There is no doubt that, in considering the liabilities of underwriters of marine insurance policies, it is a cardinal rule to regard proximate, and not remote, causes of loss. This rule is based on intention of parties as expressed in the contract into which they have entered; but the rule must be applied with good sense, so as to give effect to and not to defeat those intentions.
Per Lord Dunedin in Leyland Shipping Co Ltd v Norwich Union Fire Insurance Society Ltd [1918-19] All ER Rep 443 at p.450:
When it is a case of one of the perils acting solely and sufficiently, such as, for instance, the peril of capture, no difficulty can arise. But there are certain perils which, so to speak, pray in aid the perils of the sea. A man-of-war fires a shot and hits the ship. If it only hits the top of the bulwark or a bit of the rigging there will be at the worst only a partial average. But if the shot strikes between wind and water and makes a hole, the vessel will be sunk, and the resson of its sinking will not be the mere existence of the hole, but the fact that the sea comes in through the hole, and the vessel founders. Overwhelming by the sea is a peril of the sea in a general sense, and accordingly in such a case, if either the body of the policy or the exception were looked at alone, the peril incurred could be held to fall under either. In the exception it would fall under it, because the sinking was the direct result of the action of the man-of-war. In the body of the policy it would be immaterial whether it fell within the general expression "perils of the sea" or the particular expression "man-of-war." But the moment that the two clauses have to be construed together, it becomes vital to determine under which expression it falls. The solution will always lie in settling as a question of fact which of the two causes was what I will venture to call (though I shrink from the multiplication of epithets) the dominant cause of the two. In other words, you seek for the cause proxima, if it is well understood that the question of which is proxima is not solved by the mere point of order in timed In the illustration I have given no one would have the slightest doubt the dominant cause was the shot of the man-of-war. I would also like to remark that this class of competition between causes can only truly arise when you have to deal with an exception.
Per Lord Shaw at pp.453-454:
In my opinion, accordingly, proximate cause is an expression referring to the efficiency as an operating factor upon the result. Where various factors or causes are concurrent, and one has to be selected, the matter is determined as one of fact, and the choice falls upon the one to which may be variously ascribed the qualities of reality, predominance, efficiency. Fortunately, this much would appear to be in accordance with the principles of a plain business transaction and it is not at all foreign to the law.