Proximate cause
Category: Claims and policy principles · Reviewed by the Apex broking team · Last reviewed 2026-08-21 · ~3 min read
Category: Claims and policy principles
Also known as: causa proxima, dominant cause, efficient cause
Related concepts: trigger clause, subrogation
Definition
An insurance policy responds to loss caused by the perils it insures. Proximate cause is the rule that identifies which of the several events leading to a loss counts as its cause for that purpose. The classic statement is section 55(1) of the Marine Insurance Act 1906: subject to the policy, the insurer is liable for any loss proximately caused by a peril insured against, and is not liable for any loss which is not proximately caused by a peril insured against. Although the section is marine, the principle it codifies applies across English insurance law.
Dominant, not last in time
The leading authority is Leyland Shipping Co Ltd v Norwich Union Fire Insurance Society Ltd [1918] AC 350, where a torpedoed vessel reached harbour, was moved to a berth and later broke her back and sank. The House of Lords held the proximate cause was the torpedo, not the final grounding: proximate means proximate in efficacy, not in time. The search is therefore for the dominant, effective or operative cause — the event that, in common sense terms, really brought the loss about.
Concurrent causes
Losses often have more than one cause. Where two causes operate concurrently and one is clearly dominant, the dominant cause governs. Where neither is dominant and one of them is expressly excluded, the position is settled by Wayne Tank and Pump Co Ltd v Employers Liability Assurance Corporation Ltd [1974] QB 57: the exclusion prevails and there is no cover. The reasoning is that the parties have agreed the insurer will not pay for loss involving that peril, and a loss caused equally by an excluded peril is within that agreement. The practical consequence is that exclusions carry more weight in a causation argument than insuring clauses.
The Supreme Court revisited causation in Financial Conduct Authority v Arch Insurance (UK) Ltd [2021] UKSC 1, the business interruption test case. On disease clauses the court accepted that a loss can be caused by a large number of individually insufficient but jointly sufficient causes, so that each occurrence of disease within a defined radius was a cause of the loss even though none of them was necessary on a strict “but for” analysis. The case shows that the causation question always begins with the words the parties actually used, and that a rigid “but for” test is not the whole of English insurance causation.
Remoteness and old causes
A cause does not stop being proximate simply because it is old. In Allianz Insurance plc v University of Exeter [2023] EWHC 630 (TCC) a Second World War bomb was found during construction and detonated in a controlled explosion that damaged nearby buildings. The court held the proximate cause of the damage was the dropping of the bomb, an act of war, so the war exclusion applied and the loss was not covered; the decision was upheld on appeal. The case is a reminder that exclusions can reach back a long way when the causal chain is unbroken.
How wordings change the test
Proximate cause is a default rule and the parties can displace it. Exclusions drafted as “directly or indirectly caused by”, “arising out of” or “in connection with” are intended to catch causes that would not qualify as proximate, and English courts give those words their ordinary width. Conversely, insuring clauses that require damage to be “solely and directly” caused by a peril narrow the cover. Reading the causal language in the insuring clause and in each exclusion is therefore part of assessing whether a policy actually responds.
Why it matters
Most contested claims are causation arguments in disguise. The peril that is easiest to describe is rarely the one that decides the outcome, and the drafting of an exclusion often matters more than the breadth of the insuring clause. Causation also interacts with the policy trigger clause: a policy responds only if the insured event both falls within the trigger and is proximately caused by an insured peril.
Frequently asked questions
Does proximate cause mean the most recent cause of a loss?
No. English law looks for the dominant and efficient cause rather than the last event in the chain, following Leyland Shipping v Norwich Union [1918] AC 350.
What happens if an insured peril and an excluded peril both cause the loss?
Where the two causes operate concurrently and neither is dominant, the Wayne Tank principle means the exclusion prevails and the claim is not covered.
Can the policy wording change the causation test?
Yes. Phrases such as 'directly or indirectly caused by' or 'arising out of' widen an exclusion beyond proximate cause, while 'solely and directly caused by' narrows an insuring clause.
Related entries
This entry is part of the Apex Insurance Wiki. Last reviewed 2026-08-21. Next review: 2027-02-21. It is general reference information about UK insurance law and market practice, not regulated advice on a specific policy.
Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority (FRN 724952). This page is general information, not advice on a specific policy.