He held the Iron Cross authorized by Hitler and was made a member of the Order of the British Empire, commanded a network of 27 active spies, and was paid the modern equivalent of over six million dollars by the Nazis. Yet Juan Pujol Garcia never fired a weapon, and every one of those 27 spies was a complete fabrication. We explore how an eccentric Spanish poultry farmer with zero intelligence training pulled off the greatest con in espionage history, armed with invisible ink, a British railway guide, and a relentless imagination.

We trace his path through the trauma of the Spanish Civil War, his rejection by the British, and his decision to first dupe German intelligence from Lisbon using tourist guides and library books. We unpack how MI5 scaled his operation into Operation Fortitude, feeding the Germans a phantom army at Pas de Calais and convincing the high command that Normandy was only a diversion, keeping divisions idle for weeks after D-Day.

• How a British railway timetable became a tool for faking troop movements
• The index-card system MI5 used to track 27 fictional sub-agents
• How a killed-off agent earned his fake widow a real Nazi pension
• The 3 a.m. D-Day warning timed so the Germans would receive it too late
• How he faked his own death and retired to anonymity in Venezuela