MCWILLIAMS v SIR WILLIAM ARROL & CO LTD [1962] 1 WLR 295 The facts of the case appear sufficiently in these extracts from the judgment of Viscount Kilmuir LC, beginning at p 296:

On 27 May 1956, the deceased was employed by the first respondents as a steel erector in connection with the steel latticework tower of a tower crane which they were constructing for the use of the second named respondents in their Kingston shipbuilding yard, Port Glasgow. The deceased was an experienced steel erector ... While it was not established exactly what the deceased was doing at the time of the accident, it is not disputed that he fell from about the point where the staging was being erected to the ground, sustaining fatal injuries, that immediately after the accident one of the needles of the staging was observed to be markedly canted downwards towards the outer end and that there was found on the ground, close to the deceased’s body, a wooden plank, which had probably prior to the accident been resting on the protruding ends of the needles and also an outrigger lashing. Safety belts, the wearing of which would have prevented the death of the deceased, had been available until two or three days before the accident but were then removed to another site.