A wealthy playboy, incorrigible womaniser and dedicated gambler, Dusko Popov was one of Germany's most trusted spies, one of Britain's most successful double agents, and, some say, the inspiration for James Bond. With full access to FBI and MI5 records, along with private family papers, his incredible adventures can now be told authoritatively for the first time. Recruited by the Abwehr in 1940, 27-year-old Popov immediately offered his services to the British. His wry code-name was Tricycle, said to derive from his proclivity for nocturnal threesomes. Throughout the war he fed the Germans with a constant stream of military 'intelligence', all vetted by MI5, and came to be viewed as their most important and reliable agent in Britain; the information he supplied about the strength of the British armed forces after Dunkirk influenced German estimates for the remainder of the war. But when, in June 1941, he was ordered by the Abwehr to the United States to report on the defences at Pearl Harbour, J. Edgar Hoover, Director of the FBI, failed to heed his warnings, distrusting all spies and detesting Popov in particular, whom he considered to be 'a moral degenerate'. Tricycle went on to build up a network known as the Yugoslav Ring, which not only fed a stream of false information to Berlin but also supplied vital intelligence to the Allies on German rocketry, strategy and security. When MI5 became concerned about his extravagance and debts, a report noted his financial problems were 'no doubt connected with transactions that took place at the casino.' And when Popov asked for an immediate supply of chocolates and nylons, ostensibly to use as bribes, MI5 laconically observed, 'it is probable that the chocolates are intended to delight the interiors of those same exteriors which Tricycle wishes to decorate with stockings.' After the war Dusko Popov was granted British citizenship and awarded an OBE. The presentation was made, appropriately, in the cocktail bar at the Ritz.