Commodore Robert G. Thelwell describes what happened in his 1961 autobiography, I Captained the Big Ships:
The barman had a passion for turkish baths, but the ship's turkish baths were, of course, strictly out of bounds to all members of the crew. That did not unduly worry the barman, however. In some way, he discovered the hiding place of the key and so was able to use the baths late at night at the end of his duty. Alone in the scalding steam-room one night, the barman collapsed, and the attendant next morning discovered what was more like a piece of boiled pork than the corpse of a barman.
Staff Captain C.M. Wray (nicknamed X-ray by the crew) felt responsible for what had happened. He felt that he should have done a better job at hiding the key, and so he started sleeping with it under his pillow for good measure.
What is particularly interesting about this is that it is not an isolated incident. The Queen Mary's log notes how in 1936 - shortly after her maiden voyage - a barman was found similarly boiled to death inside the Cabin Class Turkish baths.
References: Commodore Robert G. Thelwell, I Captained the Big Ships (London: Arthur Barker Limited, 1961), 55.