Fleming’s role is important to acknowledge and important to keep in proportion. The Trout Memo established the intellectual existence of the concept. It did not design the operation, identify the body, create the identity, write the documents, arrange the delivery, manage the Spanish intelligence chain, or oversee the aftermath. Fleming’s contribution was the seed of an idea. The operation itself was built by other people over many months of detailed, unglamorous work.
The specific proposal for Operation Mincemeat came from Flight Lieutenant Charles Cholmondeley, an officer working in the intelligence section of the Air Ministry who had a secondment to MI5’s B1a section. Cholmondeley’s proposal, submitted in 1942, drew on Fleming’s earlier concept but added crucial specifics: the dead man should be a military courier, the documents should be the kind that a courier would carry between senior officers, and the body should be deployed in a location where tides or geography would carry it naturally to a coast where Spanish authorities would recover it.
The proposal reached the Twenty Committee — the double-cross committee, known informally as the XX Committee, which oversaw British double-agent operations — and found a receptive audience. The committee’s chairman, J.C. Masterman, recognized the potential. The proposal was passed upward to the London Controlling Section, the body responsible for coordinating British strategic deception operations, and then to senior intelligence and military leadership.
Ewen Montagu, a barrister in civilian life who was serving as a naval intelligence officer in the section that dealt with enemy intelligence services, was brought in to develop the proposal into an actual plan. Montagu became the principal architect of the detailed operation. He was the person who had to solve the practical problems: finding a body, creating a credible identity, writing convincing documents, establishing a plausible reason for the man to be carrying the documents, identifying the delivery point, and arranging for the body to reach that delivery point.