Louis de Wohl, a self-styled "modern Nostradamus", worked as a propagandist during World War II for Britain's Special Operations Executive, a clandestine outfit that was responsible for operations behind enemy lines.
But while his work for the British government has long been known – and his credentials questioned by astrologers – the secret files reveal the extent to which the country's spymasters disapproved of the appointment.
Britain's overseas espionage service, MI6, was outraged at De Wohl's claim that Nazi dictator Adolf Hitler could be defeated by exploiting his supposed belief in astrology.
"One of our senior officers comments that he cannot believe that anyone is going to re-employ this dangerous charlatan and confidence trick merchant," the agency said, according to the newly released files.
Another agent from the domestic intelligence agency, MI5, described De Wohl as an interloper with a "mysterious, if not murky, past" who revelled in his status as an army captain.
"None of his predictions materialized, except his forecast of Italy's entry to war, which he made at a time when this became quite patent," the officer added.
De Wohl's MI5 case officer also expressed concern that the astrologer's advice was being taken seriously, not least by SOE chief Charles Hambro. "The danger is that all this sort of pseudo-science is most insidious, and, unless you have a complete sceptic or a very strong-minded man dealing with it, quite the wrong point of view may be indulged in," he wrote.
De Wohl, who was born Lajos Mucsinyi Wohl in Berlin in 1903 to Hungarian parents, scraped a living writing pulp fiction in Germany before fleeing to Britain in 1935 as Hitler's purge of Jews gathered pace. Changing his name to Louis De Wohl and claiming to be the son of a Hungarian nobleman, he reinvented himself as an astrologer of some repute, inveigling his way into high society, where he attracted the attention of government.
In a memo to Hambro, who considered him "a perfectly splendid chap", De Wohl outlined a proposal to "shadow" the work of Hitler's personal astrologer, Karl Ernst Krafft, to find out what advice he was receiving.
"Checking up on the events of the past, I found that all major enterprises of Hitler since he came to power have been undertaken under 'good spects',” he told Hambro.
"Hitler's 'divine intuitions' are in reality simply knowledge about planetary tendencies. This opens, of course, many possibilities from the psychological point of view. An attack against Hitler at a time when he knows that his aspects are bad will certainly find him prone to some amount of defeatism. To force his hand then would be a definitive advantage for us."
Professor Christopher Andrew, who is writing the official history of MI5, said both Hambra and Britain's most senior intelligence body, the Joint Intelligence Committee, had displayed a misplaced belief in De Wohl.
"Hitler regarded astrology as complete nonsense, but the belief that he really paid attention to horoscopes entered Whitehall," he said.
"The JIC realized there was something they couldn't understand about Hitler. He didn't behave like other people. One explanation – it turned out to be completely wrong – was that he was listening to astrologers."