On April 30, 1943, José Antonio Rey María, a Spanish fisherman, rowed his skiff into the Atlantic off Andalusia. The war had barely touched this neutral coast, though debris sometimes drifted ashore. Around midmorning, he saw what appeared to be a dead porpoise but realized it was a decomposed corpse in uniform, floating face down in a life jacket. José hauled the body—accompanied by a chained briefcase—onto his boat and rowed to shore. On La Bota Beach, he and fellow fisherman Pepe Cordero dragged the remains to the dunes, where local children gathered. One noticed a silver cross around the dead man’s neck, suggesting he was Catholic. An officer from the local defense unit posted guards and arranged transportation. José, unaware of the significance of his discovery, returned to fishing.

Two months earlier, in Room 13 beneath the Admiralty in Whitehall, two British intelligence officers puzzled over how to create a fictional dead spy. The basement housed Section 17M, a top-secret unit handling the war’s most sensitive intelligence. The pair was refining the details of a deception operation unlike any attempted before. The washed-up corpse was an elaborate fraud, carrying false documents designed to mislead the enemy. The lies would travel from London through Madrid to Hitler’s desk.

Admiral John Godfrey, Britain’s director of naval intelligence, compared wartime deception to the patient trap-setting of fly-fishing. On September 29, 1939, he distributed the “Trout Memo,” actually written by his assistant, Lieutenant Commander Ian Fleming, later the creator of the James Bond novels. The memo contained 51 proposed schemes for deceiving the Germans. The 28th idea suggested dropping a corpse dressed as an airman, carrying false documents, on an enemy coast to simulate a parachute accident. The concept originated from Basil Thomson’s 1937 detective novel The Milliner’s Hat Mystery.

In late September 1942, this theoretical plan gained momentum when a British Catalina seaplane crashed off Cádiz, Spain. Paymaster-Lieutenant James Hadden Turner died carrying a letter revealing the November 4 date for the Allied invasion of North Africa. Officially neutral, the Spanish authorities returned the body and letter to Britain, and forensic examination concluded the documents had not been tampered with. However, another crash victim, French intelligence officer Louis Daniélou, had carried documents that were copied and passed to the Germans, who dismissed them as unimportant. The incident proved the Spanish could serve as conduits to German intelligence.

Flight Lieutenant Charles Christopher Cholmondeley, an eccentric MI5 officer with poor eyesight that prevented him from flying, seized on this precedent. Serving as secretary to the XX (Twenty) Committee, which oversaw double agents under chairman John Masterman, Cholmondeley presented his Trojan Horse plan on October 31, 1942: A corpse with water-filled lungs and false documents would be dropped near Spain to wash ashore in enemy territory. The committee identified Spain as ideal, expecting that religious considerations might limit autopsies.

This type of deception, known as the “haversack ruse,” dates to 1917, when Richard Meinertzhagen deliberately lost a bag of false plans to deceive Turkish forces before the battle of Beersheba. Other wartime variants had been attempted, including Peter Fleming’s unsuccessful Operation Error in Burma. The central problem remained: Little evidence existed that the haversack ruse actually worked.

John Masterman, the Twenty Committee chairman, approved Cholmondeley’s plan and assigned Lieutenant Commander Ewen Montagu, their Naval Intelligence representative, to assist. Montagu volunteered to obtain a suitable corpse and address the medical challenges. His organizational skills complemented Cholmondeley’s creativity.

Born in 1901 to the wealthy Jewish banking family of Baron Swaythling, Montagu grew up in London. His elder brother Stuart was conventional, while his younger brother Ivor became a communist filmmaker who founded the International Table Tennis Federation and worked with Charlie Chaplin. At Cambridge, Ewen and Ivor helped popularize table tennis. After marrying Iris Solomon in 1923, Montagu became a successful barrister, made King’s Counsel in 1939.

When war erupted, Iris and their children, Jeremy and Jennifer, evacuated to America. Montagu joined the Royal Naval Volunteer Reserve and was recruited by Admiral Godfrey into Naval Intelligence. He was assigned to lead Section 17M from Room 13, a cramped basement beneath the Admiralty. His unit, including formidable assistant Joan Saunders, handled “Ultra” intelligence—decrypted German Enigma signals—analyzing and disseminating up to 200 top-secret messages daily. Montagu became an expert at reading enemy intelligence traffic and was placed in charge of all deception involving double agents. In New York, Iris worked for British Security Co-ordination, the UK’s intelligence hub in the United States, under spymaster William Stephenson. She demonstrated personal courage in 1940 by offering to pose as a British officer willing to sell a false minefield chart to the Germans.

In Room 13, Montagu and Cholmondeley began developing the deception plan in earnest.

At the Casablanca Conference in January 1943, Churchill and Roosevelt designated Sicily as the next Allied target. On January 22, Operation Husky was formally approved, with General Eisenhower in command. Sicily’s strategic position controlling Mediterranean access made it an obvious choice for attack: too obvious. Churchill acknowledged that anyone could predict the invasion site, requiring a massive deception to prevent German reinforcement. 

Lieutenant Colonel John H. Bevan, head of the London Controlling Section responsible for coordinating strategic deception, developed Operation Barclay, designed to convince the Axis powers that the Allies would invade Greece and Sardinia instead of Sicily. Bevan worked with Lieutenant Colonel Dudley Wrangel Clarke, chief of the Mediterranean-based “A” Force deception unit. Despite the scheme, a German intelligence report from early February still correctly identified Sicily as the likely target. Operation Barclay would exploit the German command’s tendency toward wishful thinking and institutional “yesmanship,” i.e., inventing reports their superiors wanted to hear and believing intelligence that confirmed preconceptions. The deception would involve creating fake armies, deploying double agents, and orchestrating false troop movements.

Meanwhile, Montagu and Cholmondeley faced the practical challenge of obtaining a suitable corpse for Operation Mincemeat. They needed a fresh, military-age male without obvious injuries, whose cause of death would withstand scrutiny, and whose next of kin would not object. Montagu consulted Sir Bernard Spilsbury, Home Office pathologist. Spilsbury advised that victims of air crashes at sea often died from exposure or shock rather than drowning or trauma, broadening their options. The simplest solution would be an actual drowning victim who could float ashore in a life jacket.

Montagu approached Bentley Purchase, a St. Pancras coroner who had previously assisted intelligence by falsifying death certificates. Purchase explained he could legally issue a burial certificate for a body supposedly being sent abroad, giving him discretion over its disposal. After Montagu falsely assured him the plan had the prime minister’s approval, Purchase promised to keep a lookout for a suitable candidate.

On January 24, Montagu worked late at his family home in Kensington, aware that the Allies’ Casablanca Conference planning, January 14-24, had accelerated his timetable. That same evening, a young Welshman in another part of London died after ingesting rat poison.