Proximate Cause

The foundational statutory statement of the proximate cause rule in English insurance law is section 55 of the Marine Insurance Act 1906, which, although framed for marine insurance, has long been treated as expressing a general principle of insurance law. Section 55(1) provides that 'the insurer is liable for any loss proximately caused by a peril insured against, but, subject as aforesaid, he is not liable for any loss which is not proximately caused by a peril insured against.' This means that where a loss has more than one contributing cause, the policy responds only if the dominant, effective cause was itself an insured peril — not merely any cause that happened to be present in the chain of events, and not a cause that is merely the last event in time.

Section 55(2) then sets out particular applications of the rule, including that, 'unless the policy otherwise provides, the insurer on ship or goods is not liable for any loss proximately caused by delay, although the delay be caused by a peril insured against', and that the insurer is not liable for 'ordinary wear and tear, ordinary leakage and breakage, inherent vice or nature of the subject-matter insured'. The section also confirms that an insurer remains liable for a loss proximately caused by an insured peril 'even though the loss would not have happened but for the misconduct or negligence of the master or crew' — reinforcing that the proximate cause enquiry looks to the operative peril, not simply to whether some other negligent or excluded factor also played a part.