Obituary: Jean Leslie, MI5 operative whose photograph played a key part in a counter-intelligence mission Born: 20 November, 1923, in Hampshire. Died: 3 April, 2012, in Berkshire, aged 88 Jean Leslie's photograph in 1943 totally deceived the German High Command and led to one of the most audacious hoaxes of the Second World War. Operation Mincemeat was devised in the spring of 1943 by two gifted intelligence officers, Flight Lieutenant Charles Cholmondeley of MI5 and Commander Ewen Montagu of Naval Intelligence. The Allies were planning to invade Italy through Sicily from North Africa and Winston Churchill demanded some inspired subterfuge from the Secret Service that would leave the Germans guessing about the true nature of the Allies" plans. Flt Lt Cholmondeley and Cdr Montagu dreamed up the idea of planting false papers on an "officer" whose body was then found in the Mediterranean carrying a briefcase padlocked to his wrist with top secret plans that clearly showed the Allies would invade through Sardinia and Greece. The body had to be given official documents with a cast-iron identity. A cadavre was obtained from the London coroner - that of a Welsh vagabond called Glyndwr Michael. His body was kept in the morgue while a fictitious existence was concocted. Scrupulous planning involved authentic military passes and name - Major William Martin, an expert in amphibious warfare. To make it as convincing as possible, there was also a letter from his father, a warning about his overdraft from his bank manager, a bill for an engagement ring and some love letters. Accompanying them was a delightful black and white photo of Major Martin's fiancée, "Pam" . The Secret Service asked the girls in MI5 to submit personal photos and the one of Jean Leslie was just what they wanted. It had been taken the previous summer on the Thames in Oxfordshire while she was enjoying a week-end off. It showed an attractive girl in a one-piece swimsuit, with dishevelled hair, drying herself with a bath towel. It captured the relaxed idea of a couple enjoying a day in the sun and was just the sort of photo a fiancé would carry in his wallet. Leslie became Pam, a girl working in a government office who had met Major Martin five weeks earlier. Leslie's contribution to the subterfuge was increased when Cdr Montagu decided to create a real identity for Major Martin. "He was Willie and I was Pam," Leslie recalled years later. We went to clubs, films and dinner - always keeping tickets stubs etc. She also inscribed the swimsuit photograph with a loving, "Till death us do part. Your loving Pam. The entire operation was an overwhelming success. The body was picked up by a fisherman and the contents of the briefcase were leaked to the German SS in Madrid. Its operatives deemed it important and forwarded the contents to Hitler in Berlin. The briefcase was then returned to the seashore and immediately returned to MI5 in London. The vital question was whether the documents inside a sealed envelope had been opened. The Germans had covered their tracks expertly. The scientists at MI5 confirmed there was no doubt that the plans had been read. German troops were redeployed to Greece and Sardinia, while Sicily was left sparsely defended. A triumphant telegram was sent to Churchill: "Mincemeat swallowed rod, line and sinker." Nancy Jean Leslie was the daughter of Sir Norman Leslie, Bt, a director of Cable & Wireless, and although she had no formal education she spoke good French, which probably accounted for her employment at MI5. She had lived in Paris on the death of her father with her mother. But when Paris was overrun by the Germans in 1940, she returned to London. She worked in MI5 throughout the war, mostly in counter-intelligence and the double agent section of MI5 at Ham, Surrey, where enemy spies were interrogated. After the war, she married Colonel William Gerard Leigh, an officer in the Life Guards and an expert horseman. He became chairman of the Guards Polo Club and the couple travelled widely - especially to Palestine. Leigh involved herself in her husband's work and with charities such as the Docklands Settlement and the Elizabeth Garrett Anderson Hospital, in London. Always an enthusiastic gardener she much improved their various homes in Berkshire. In 1953, Cdr Montague published, The Man Who Never Was, a book about Operation Mincemeat, which became a bestseller. Two years later there was an equally successful film made, starring Clifton Webb. But Leigh resolutely refused to talk about the operation and only in 1996, when more precise details emerged, did she admit publicly that Jean Gerard Leigh and Pam were one and the same person. Jean Gerard Leigh's husband died in 2008. She is survived by her two sons and two daughters.