The Welshman Arthur Owens (alias ‘Snow’ for MI 5, ‘Johnny’ for the German Abwehr) is probably the best known double agent in the ‘XX System’, the deception game played by British counter-intelligence against the Abwehr, the German military intelligence service. He is not the first double agent who is the ‘hero’ of a book. Some of them published more or less credible autobiographies. Others, like ‘Snow’, were already mentioned in Masterman’s ‘XX System’ or in an inaccurate book written by Ladislas Farago, ‘The game of the foxes’.