Breaking the chain (or novus actus interveniens, literally "new act intervening") refers in English law to the idea that causal connections are deemed to finish. Even if the defendant can be shown to have acted negligently, there will be no liability if some new intervening act breaks the chain of causation between that negligence and the loss or damage sustained by the claimant. Discussion
Where there is only a single operative cause for the loss and damage suffered by the claimant, it is a relatively simple matter to determine whether that cause was a breach of the duty of care owed to the claimant by the defendant. But where the sequence of events leading to the loss and damage comprises more than one cause, the process of separating and attributing potential or actual liability is more complicated.
Act of God and other natural events as contributing causes
Where there are several potential causes of harm, some of which are tortious and some of which are natural, the basic rule is that the claimant can succeed only if he or she proves on the balance of probabilities that the loss and damage is attributable to the tort: Wilsher v. Essex Area Health Authority [1988] AC 1074. In The Oropesa [1943] 1 All ER 211 a collision occurred in heavy seas between the Oropesa and the Manchester Regiment which was so seriously damaged that the captain sent fifty of the crew to the Oropesa. An hour later, he set off with sixteen of the crew to go to the Oropesa in another lifeboat. This lifeboat capsized in the heavy seas and nine of the crew drowned. The Manchester Regiment later sank. Relatives of the drowned seamen sued. The question was whether the action of the captain in leaving the Manchester Regiment broke the chain. It was held that the captain's action was the natural consequence of the emergency in which he was placed by the negligence of the Oropesa and, therefore, the deaths of the seamen were a direct consequence of the negligent act of the