A glamorous Russian ballerina who worked as a Nazi spy is the subject of an MI5 file revealed for the first time this week.
Marina Lee, an agent in Norway, was "blond, tall, with a beautiful figure, refined and languid in manner".
She was suspected of infiltrating the headquarters of General Claude Auchinleck in 1940.
Lee reportedly got hold of a key battle plan which she passed to the German commander.
British, French and Norwegian troops under General Auchinleck were later defeated at the Battle of Narvik and forced to withdraw from German-controlled Norway.
The Russian-born Lee, whose maiden name was Alexievna, went missing in Spain after the war and one note expresses fears she may have gone to work for the Soviets.
"She is in fact the type to transfer her allegiance having once had a taste of the game," said a note on her file.
Dr Ed Hampshire, the principal records specialist at the National Archives, said: "Marina Lee was in Norway at the time that Germany invaded and fought the Allies in Norway. It ended up being a disaster for the British."
He said she was thought to have infiltrated the British headquarters at Tromso and added: "It's a classic femme fatale story, if it's true.
"It's not confirmed that it was true but it could be Auchinleck or his staff were seduced or persuaded by this lady to hand over the battle plan.
"It's something that could almost come out of a pulp novel of the time," said Dr Hampshire.
The file describes Marina Lee as being a ballerina, born in St Petersburg in 1902, who married a Norwegian in the 1930s.
She seems to have left quite an impression on a number of German officers who had been in contact with her and were later interrogated by MI5 at their base, Camp 020, in Richmond, south west London.
One of them, Finckenstein, described her as "blonde, tall, with a beautiful figure, refined and languid in manner".
Another report, in French, describes her as "slim, very blonde (natural), blue grey eyes, very pretty legs".
Sadly no photograph of her remains on the file as Finckenstein threw the last remaining one into the sea when he was seized off the coast of Norway.
While Marina Lee existed in the shadows, another suspected spy in the MI5 files lived openly in Finsbury Park, north London, and frequently expressed her support for Hitler.
Margaret Newitt, who ran a London agency for German and Austrian domestic servant girls, was interned in 1940.
MI5 suspected she was working with the German Embassy to plant spies in the homes of key people in London.
The widow's MI5 file includes a letter she wrote to the Daily Express in 1936.
She wrote: "Only people what have been in Germany three years ago can fully appreciate what Hitler has done for Germany.
"If Germany wants to get rid of the Jews, let them. It is entirely their own affair and I am sure we can do with a few more."
Perhaps unsurprisingly MI5 kept a close watch on her and her agency.
One MI5 officer wrote: "There is no doubt that she knew perfectly well that the employment agency was being used by the German Embassy to send people into this country who might be useful to the German government."
In October 1940 she was arrested and interrogated at Holloway prison in north London.
She admitted she had applied in 1936 to become a member of the Nazi Party and the file adds: "This was a rather strange thing for a loyal British subject to be doing."
The officer adds: "I scarcely think that I need add anything more in order to show that Newitt is a dangerous woman deeply involved in the Nazi cause, who has prevaricated and lied in order to evade the appropriate action."
Soon afterwards the Home Secretary, Herbert Morrison, signed an order detaining her indefinitely.
On her file it states: "Mrs Newitt said that she would welcome internment, not because she had done anything wrong, as she had a clear conscience, but she was at her wits' end for livelihood."
She is thought to have been freed after the war but it is not clear what became of her.