They soon regretted it.
The file released to Britain's National Archives catalogs the frustrations of MI5 handlers as they tried to prevent the astrologer, Louis de Wohl, from publicly embarrassing high-ranking intelligence and military officers.
"I have never liked Louis de Wohl - he strikes me as a charlatan and an imposter," reads the first line in the astrologer's file. The letter is typical and appeared to be signed by Dick White, who went on to become the head of Britain's domestic spy agency, MI5, in the 1950s.
That view didn't keep de Wohl from winning a temporary rank as a British army captain. He was sent by Prime Minister Winston Churchill, who did not believe in astrology, to the U.S. to persuade Americans that the Nazis would lose within months if they entered the war.
When de Wohl's services were no longer needed, intelligence agents puzzled over how to get rid of the man who called himself Britain's state seer, the declassified documents show.
De Wohl was born in Berlin in 1903 and fled to Britain in 1935 to avoid Nazi persecution for being part Jewish. His wife, Alexandra, fled to Santiago, Chile, where she claimed to be a Romanian princess and was known as "La Baronessa."
In London, de Wohl claimed variously to be a Hungarian nobleman, the nephew of an Austrian conductor, the grandson of a British banking magnate and a relative of the Lord Mayor of London. His break came, he wrote in a later book, during a dinner at the Spanish Embassy, when a Spanish duchess asked de Wohl to reveal Hitler's horoscope to Britain's foreign secretary, Lord Halifax.
Sir Charles Hambro, the head of Britain's Special Operations Executive, soon hired de Wohl as part of his network of agents across Europe.
The government rented the astrologer a hotel apartment on London's exclusive Park Lane. There, de Wohl wrote horoscopes for Allied and Nazi leaders on paper with the letterhead "Psychological Research Bureau."
But de Wohl's predictions were often vague. His December 1942 prediction read: "The German astrologers must pray that enemy action does not force the Fueher into making important decisions within the first eight days of the month (of July), as this would lead to great disaster."
Agents complained de Wohl's flamboyant demeanor was destroying their carefully constructed cover story that his apartment was paid for by a wealthy female patron and that his special operations liaison officer was a mistress. Agents also complained of his boasting about connections to the War Office and Naval Command.
His task in the U.S. was to counter a convention of pro-German astrologers that had predicted Hitler would win the war. Billing himself as "The Modern Nostradamus," de Wohl proclaimed the stars showed the opposite - that Hitler would lose.
Ultimately it was Japan's attack on Pearl Harbor on Dec. 7, 1941, that brought the U.S. into the war - not de Wohl's assurances that President Franklin Roosevelt had a stunning horoscope.
His services no longer needed, de Wohl was called back to London in February 1942. He returned to find his hotel apartment stripped bare and his "department" disbanded.
According to the released MI5 correspondence, senior officers offered a number of proposals on how to "dispose" of de Wohl, including interning him in a camp or moving him to a remote corner of the country. Two other options are blanked out.
Deciding de Wohl was potentially damaging the reputation of his employers, MI5 decided to keep him happy and continue to employ him.
But even Hambro had tired of the astrologer.
"I have no doubt if I checked up his successes, I would see that he had more than an equal number of failures, but I have not the inclination nor the time to do so," Hambro wrote.