Operation Mincemeat, BBC Two

They have period names in the foreign country we call the past. In last night’s documentary about a brilliant wartime trick practised upon Hitler, we came across a coroner called Sir Bentley Purchase, a love interest called Peternel Hankins and a Welsh tramp with the stirringly patriotic if implausible name of Glyndwr Michael. Charles Cholmondeley, one of the authors of the deception, would even draw attention to the absurd discrepancy between the way his name looked and sounded. More or less the only person in this entire story who didn't sound like a character in a novel was Major Bill Martin, and yet he was entirely fictional. How on earth did the Nazis not smell a rat?

In Operation Mincemeat, Ben Macintyre was last night granted an hour of primetime to boil down his book of the same name. It told the story of what he called “perhaps the greatest military hoax since the Trojan Horse”. The corpse of a Royal Marine was found floating in the waters off southern Spain in late April, 1943. Documents located about his person, once photographed and carefully studied, made their way back to Berlin, among them a top-secret letter which persuaded Hitler that the Allies were planning to invade Southern Europe via Greece rather than the blindingly obvious option of Sicily.

In fact this was no marine but a Welsh vagrant, a sad victim of the collapse of the mining industry in the 1930s, who had committed suicide a couple of months earlier by taking rat poison. Rat poison being undetectable, he was the perfect specimen for Mincemeat: the real cause of death would not show up in an autopsy. The idea to deploy a dead body in the war effort originally belonged to a young intelligence officer called Ian Fleming (coincidentally a walk-on character over on the other side in Any Human Heart), and it was taken up with enthusiasm by two colleagues possessing what Churchill admiringly called “corkscrew minds” - the ability to think round corners.

Cholmondeley and Ewen Montagu, a fiendishly shrewd barrister turned naval intelligence officer, took on the task of creating a back story for Major Martin. As well as giving him a sizeable debt at the Midland Bank, they invented for him a thriving romance with a young woman called Pam. There was a love letter from her, in fact composed by a desiccated spinster in the War Office, a receipt for a diamond ring and a comely photograph of Pam posing shyly in a swimsuit by a river.

“Pam”, it turns out, is still alive. Her real name is Jean Leslie. An employee of MI5 in 1943, 67 years on she is in a wheelchair, but still game as anything. “We were all rather good secret keepers,” she told Macintyre, and she flatly refused to tell him anything else. Operation Mincemeat was as good as historical documentary is allowed to be nowadays, and it was made just in time. The men involved are all no more (an audio interview with the submarine commander who dropped the body off in Spain was from 2003). But a couple of the wonderful women who worked in the War Office are still with us, partly because they were recruited at such a heartbreakingly young age. Even Cholmondeley was only 25 in 1943.

Presumably the film rights have been snapped up and all these talking heads will live anew as young British actors being frightfully clipped in dowdy tweed. There has already been one film, adapted from Montagu’s book The Man Who Never Was (1953). Although his book purported to lay bare the facts, Montagu was partly complicit in keeping a smokescreen in place. He claimed that he had sworn to the relatives never to divulge the identity of the dead man. In fact Glyndwr Michael had no relatives. Macintyre interviewed the man who unearthed his true identity in the 1990s, and movingly concluded his film at the graveside in Huelva which now bears two names: one made up, but the other real.

Watch a clip from The Man Who Never Was (1956):

One of the strengths of the film was the sense that, in another life, Macintyre (pictured above) would have been one of the clever young chaps pulling the wool over Jerry’s eyes in the War Office or Bletchley Park, which he also visited. It was with a plucky lack of complaint that he threw himself into all the immersive tomfoolery that documentary makers nowadays deem a stylistic sine qua non: Macintyre mucking about on bikes, in boats, in cars, on the tennis court etc. A more sophisticated trope, which was only slightly irritating, found him at the theatre in a dickey bow, while up onstage the life story of Major Martin was conjured up before him by actors.

Sadly, there was no space to go into the two theatre ticket stubs planted in Major Martin’s wallet. A week before his body was found, Martin had apparently been to see Sid Field in Strike a New Note in the West End. Presumably with “Pam”. One likes to think that Hitler, as soon as the news filtered through from his undercover agents in Spain, had Nazi intelligence check up on Sid Field and ascertain to his satisfaction that he was indeed a Brummie vaudevillean currently performing in Shaftsbury Avenue. As well as Bill Martin's suspiciously ordinary name, the Reich missed another trick. The body of Glyndwr Michael was very tall for a presumably malnourished son of the Valleys. “We can confirm, mein Führer, that these theatre tickets are genuine. But how do these British fools expect us to believe that such a giant would fit into one of those cramped West End theatre seats?”

• Watch Operation Mincemeat on BBC iPlayer
• Find Operation Mincemeat: The True Story That Changes the Course of World War II by Ben Macintyre on Amazon