John Nevil Maskelyne (1839-1917) trained as a watchmaker in his native Cheltenham before becoming a stage magician and inventor of evident talent. It was Maskelyne who developed the first lock mechanism for pay toilets from which the euphemistic phrase 'to spend a penny' came. He also made it his mission to expose frauds and cheats whenever he encountered them and, in 1894, he published 'Sharps and Flats: A Complete Revelation of the Secrets of Cheating at Games of Chance and Skill'. But perhaps his greatest contempt was reserved for those who deceived by claiming supernatural powers and who w...