Chain of Causation in UK Law

Yet an anxiety neurosis or a reactive depression may be recognisable psychiatric illnesses, with or without psychosomatic symptoms. So, the first hurdle which a plaintiff claiming damages of the kind in question must surmount is to establish that he is suffering, not merely grief, distress or any other normal emotion, but a positive psychiatric illness.

For there to be a break in the chain of causation, the true cause of the loss must be the conduct of the claimant rather than the breach of contract on the part of the defendant; if the breach of contract by the defendant and the claimant's subsequent conduct are concurrent causes, it must be unlikely that the chain of causation will be broken.

It is, however, also plain that mere unreasonable conduct on a claimant's part will not necessarily do so – for example where the defendant's breach remains an effective cause of the loss, albeit in combination with the claimant's failure to take reasonable precautions in its own interest: see, for example, County Ltd v Girozentrale, per Beldam LJ (loc cit).

Fourthly, the claimant's state of knowledge at the time of and following the defendant's breach of contract is likely to be a factor of very great significance. For the chain of causation to be broken, the claimant need not have knowledge of the legal niceties of the breach of contract; nor, as it seems to me, will the chain of causation only be broken if the claimant has actual knowledge that a breach of contract has occurred – otherwise there would be a premium on ignorance.

It is quite possible that in spite of all reasonable care his leg may give way in circumstances such that as a result he sustains further injury. But if the injured man acts unreasonably he cannot hold the defender liable for injury caused by his own unreasonable conduct. The chain of causation has been broken and what follows must be regarded as caused by his own conduct and not by the defender's fault or the disability caused by it.

An explosion is only one way in which burning can be caused. Burning can also be caused by the contact between liquid paraffin and a naked flame. In the one case paraffin vapour and in the other case liquid paraffin is ignited by fire. I cannot see that these are two different types of accident. They are both burning accidents and in both cases the injuries would be burning injuries.

These cases shew that, where human action forms one of the links between the original wrongdoing of the defendant and the loss suffered by the plaintiff, that action must at least have been something very likely to happen if it is not to be regarded as novus actus interveniens breaking the chain of causation.