It is perhaps fitting that Guy Trundle was put in charge of barrage balloons in wartime London. By then, the secret lover of Wallis Simpson during the abdication crisis had proved his consummate skill at keeping a number of potentially inflammatory balls in the air at the same time.

Few men possessed the amorous dexterity of Trundle, described by Special Branch spies as “a very charming adventurer, very good looking, well bred and an excellent dancer” in a highly confidential 1935 report released last week.

His inspiration could have been Georges Feydeau, the master of bedroom farce. While Trundle was helping Simpson to cuckold Edward VIII, he was simultaneously conducting an ardent liaison with a seductive tennis player. Eileen Bennett was regarded as the Anna Kournikova of her day after revealing daring white briefs under the scandalised gaze of Princess Alice at a charity match in 1933.

The tennis player was married, but then so was Trundle. As, indeed, was “Mrs Simpson”, for whose love Edward sacrificed his throne. Such a plot would have fully stretched Feydeau’s talents. But Trundle’s love life was to take on even greater complexity.

This was his mistress Vera Emanuel, a Junoesque actress whom he visited nearly every day at her West End home whether or not her husband was present. The husband was a banker willing to make Trundle an extraordinary loan — his wife. By all accounts the menage à trois lived in perfect harmony and when Trundle was dying of cancer it was Vera who nursed him until the end.

The revelations from the Public Record Office paint a louche picture of elastic morals among the rich and titled before the austere wartime years. But an even more surreal tableau, revealing the abdication’s principal actors sleeping in connecting rooms, was revealed to The Sunday Times last week by Edward’s 83-year-old godson, William, the 4th Earl of Dudley.

In April 1936 his father, the 3rd earl, held a house party at Himley Hall near Dudley at which the leading guests were Edward VIII, Wallis Simpson, her husband Ernest Simpson (they were not yet divorced) and the latter’s girlfriend, nicknamed Buttercup. The 3rd earl was surprised to receive a visit from Queen Mary, Edward’s mother, who asked him to confirm the guests. “‘Can I have a look at the sleeping arrangements?’ said the queen. So my father took her upstairs to show her,” says the 4th earl.

“She was curious to see how it was all disposed. There was the king’s room, then the bathroom which connected to another room which Wallis was in; then another bathroom, connected to the one Mr Simpson was in, then the bathroom connected to the room which his lady friend was in. They were all connected together.”

But if infidelity was a game, what game was Special Branch playing as it diligently noted Trundle’s activities? One theory is that evidence on Trundle was passed to the cabinet as proof of Simpson’s betrayal. A word to Edward might have halted the marriage and prevented a constitutional crisis. So why was nothing said: was it deference or a more cynical calculation? Some Establishment figures, who complained that Edward lacked the necessary qualities of kingship, might have been happy to let events take their course.

Even the 4th Earl of Dudley believes Simpson unwittingly did the country a favour by removing him from the throne. “In my opinion he was totally unsuited to be king of England during a major war against Germany,” he says. “I think, therefore, that it is very fortunate the affair wasn’t brought to his attention. It sounds as if they didn’t have the nerve to tell him.”

Whatever potential role he was assigned, Trundle seems an unlikely candidate to influence history. The son of a vicar from York, he had been reduced by circumstances to working as a humble car mechanic and Ford salesman after leaving the RAF in 1927.

Special Branch, which had been shadowing Simpson since the beginning of her affair with the future king, was aware she was entertaining another lover but did not pick out the 36-year-old lounge lizard on its radar screens until several weeks later. “The identity of Mrs Simpson’s lover has now been definitely ascertained,” says a Special Branch report dated July 3, 1935. “He is Guy Marcus Trundle, now living at 18 Bruton Street. He is said to boast that every woman falls for him. He meets Mrs Simpson quite openly at informal social gatherings as a personal friend, but secret meetings are made by appointment when intimate relations take place.”

It is implicit from the records that Trundle spoke to Special Branch about the relationship. “Trundle receives money from Mrs Simpson as well as expensive presents. He has admitted this.”