With Britain braced for a German invasion, MI5 recruited an ex RNAS officer, come confidence trickster, called Walter Dicketts as a double agent. Codenamed Celery, Dicketts was sent to Lisbon with the seemingly impossible mission of persuading the Germans he was a traitor and then extract crucial secrets. Once there, the Nazis spirited him off to Germany. With his life on the line, Dicketts had to outwit his interrogators in Hamburg and Berlin before returning to Britain as, in the Nazis eyes, a German spy. Despite discovering he had been betrayed as an MI5 plant before he even left for Germany, Celery somehow got back to Lisbon. After that he persuaded an Abwehr Officer to defect, and spent nine months undercover in Brazil. A mixture of hero and crook, Dicketts was worldly and intelligent, charming and charismatic. Sometimes rich and sometimes poor, his private life was a web of complexity and deception. Using family and official records, police records, newspaper articles and memories, the author unravels the tangled yet true story of Double Agent Celery.