In Knightley v. Johns (CA, 1982) (...) it was said that, in considering whether the intervening of a third party breaks the chain of causation, the test is whether the damage is reasonably foreseeable in the sense of being a "natural and probable" result of the defendant's breach. A deliberate decision to do a positive act is more likely to break the chain than a mere omission; so too, tortious conduct is more likely to break it than conduct which is not.