A few quite interesting facts

Franz Kafka invented the workman's hard hat.
Sir Arthur Conan Doyle invented the lifejacket.
The Prime Minister of Australia went for a swim in 1967 and was never seen again.
The President of France got out of his train one night in 1920 without any trousers on.
David Owen, incidentally, has written a quite interesting article about frailties of heads of state: this fact, however, is not in itself interesting.