Mata Hari was better known for her lovers than spying achievements
Female spies using sex to obtain secrets may be a staple of espionage thrillers, but it has emerged that in reality British intelligence did not approve.
MI5 also instructed its staff on how to stop their female spies falling in love with targets, files newly-released to the National Archives show.
The advice was issued at the end of World War II by top MI5 agent-runner Maxwell Knight, the inspiration for James Bond spy chief "M".
During the war, he headed the MI5 department recruiting agents to penetrate Nazi spy rings in Britain.
Loss of interest
Like his fictional counterpart, he felt sex had no place in the serious business of espionage.
"I am no believer in what might be described as Mata Hari methods," he wrote, referring to the World War I spy known for her many lovers.
"I am convinced that more information has been obtained by women agents by
keeping out of the arms of the man, than was ever obtained by sinking too
willingly into them.
A clever woman who can use her personal attractions wisely has in her armoury a very formidable weapon
"If a man is physically but casually interested in a woman, he will very speedily lose interest in her once his immediate object is attained.
"Whereas if he can come to rely upon the woman more for her qualities of companionship and sympathy, than merely those of physical satisfaction, the enterprise will last longer."
Mr Knight felt the best way to ensure women agents did not fall in love with men they were spying on, was simply to steer them clear of their "type".
"When the officer is really getting acquainted with his agent, he should, in the case of a woman, pay particular attention to the types of men that the woman concerned likes and dislikes.
"His future direction of her should, to a very large extent, be guided by the knowledge which he has obtained during this initial period."
Knight did support the use of women agents though, dismissing a "very long-standing and ill-founded prejudice" against them.
"A clever woman who can use her personal attractions wisely has in her armoury a very formidable weapon," he said.
Members of the public can view the 280 newly-released files at the National Archives, Kew, west London.