JOSEPH SMITH (PAUPER) v CHARLES BAKER & SONS [1891] AC 325 The following extract is taken from the judgment of Lord Halsbury LC, beginning at p 334:

The objection raised, and the only objection raised, to the plaintiff’s right to recover was that he had voluntarily undertaken the risk. That is the question, and the only question, which any of the courts, except the county court itself had jurisdiction to deal with. Now, the facts upon which that question depends are given by the plaintiff himself in his evidence. Speaking of the operation of slinging the stones over the heads of the workmen, he said himself that it was not safe, and that whenever he had sufficient warning, or saw it, he got out of the way. The ganger told the workmen employed to get out of the way of the stones which were being slung. The plaintiff said he had been long enough at the work to know that it was dangerous, and another fellow workman in his hearing complained that it was a dangerous practice.