P and X were mine workers and tried to fix a dodgy roof and were told not to do any work under it until it was fixed by the owner, D. When they couldn’t fix it, they jointly decided (neither was in charge of the other) to continue their work, which meant P (but not X) going back under it, and it collapsed, killing P. X’s actions made the company liable. The HL held that P was 80% responsible and D was 20% responsible. Therefore P’s award was reduced by 80%.
Lord Oaksey: It was uncertain whether P would still have worked under the roof had X not concurred in the joint decision and therefore it is too speculative to reach the conclusion that he would not, which would raise the percentage for which D would be liable (Surely therefore it is also too speculative to conclude that he would not. What is the justification for erring on the side of D?).
Lord Reid: To establish causation we should ask “was D's fault so much mixed up with the state of things brought about by P that in the ordinary plain common sense of this business it must be regarded as having contributed to the accident.” Here it was, there being no “sufficient separation of time, place or circumstance between them to justify its being excluded”.
Lord Tucker: Only P returned to work under the roof and therefore he is more at fault than X.