National Archives: Ballerina turned spy 'cost Britain' humiliation in Norway

• General Sir Claude Auchinleck headed the defeated taskforce Picture: Getty Images

A devastating setback for the Allied cause in Europe, the fiasco surrounding the abortive campaign led directly to the collapse of Neville Chamberlain's Conservative-led government and his replacement as Britain's wartime leader by Winston Churchill.

Until now, the incompetence of allied military planners has been blamed for the forced withdrawal of the defeated taskforce, headed by General Sir Claude Auchinleck.

But classified MI5 files, made public for the first time today, suggest that a beautiful ballerina turned Nazi spy - a Second World War Mata Hari - may have been responsible for the military disaster in Norway.

The documents claim that the former ballerina, known as Marina Lee, was able to infiltrate the headquarters of the Allied taskforce and steal their battle plans for the Germans.

However the papers, released to the National Archives in Kew, also reveal that while MI5 continued to pursue the trail of the elusive Lee for more than three years after the war was over, they were never able to establish the truth of the allegations.

According to the now unclassified documents, the suggestions of Lee's involvement first surfaced two years after the withdrawal of the Allied forces from Norway.

In January 1942, Gerth Van Wijk a captured German agent now working for the British, recounted what he admitted was an "astonishing story" told to him by another captured agent called Von Finckenstein.

The German Secret Service had sent a "beautiful" woman to Auchinleck's headquarters at Tromso where she had successfully secured the Allied campaign plan. The details had then been handed to General Eduard Dietl, the commander of the German forces, who was able to rearrange his defence and to defeat Auchinleck.

Von Finckenstein told his fellow agent that the spy was Marina Lee, a married woman who was born in Russia with the maiden name Marina Alexievna.

"Her parents were killed by the Bolsheviks and she herself fled to Scandinavia where she married a Norwegian national," Van Wijk told MI5.

"She was trained in Russia as a ballerina and in Oslo was for some time the head of a school of ballet. She is a highly valued and experienced German agent."

In November, 1942, corroboration for Von Finckenstein's story appeared to come from another captured German agent, KC Hansen, who was detained at the Camp 020 interrogation centre in London

"Hansen knew Marina Lee had discovered Auchinleck's plans during fighting in northern Norway and revealed them to Dietl who had thereupon defeated him," MI5 reported. "In fact he confirmed the remarkable story told by Finckenstein."

No fresh information emerged until after the end of the war when another German agent, called John Dollar, also claimed to have known Lee.

He revealed that, after carrying out numerous missions in Norway, Lee was then sent to neutral Spain to spy on Allied officers frequenting one of Madrid's luxury hotels.

She appeared to have remained in Spain until the end of the war, and in 1947 an all ports bulletin was issued with instructions for MI5 to be alerted immediately if she could be traced.

One MI5 officer wrote: "In view of Lee's pre-war Soviet ties, I think it is fair to continue to regard her as a potential threat to security."

Lee, however, never surfaced again, leaving the claims of her remarkable feats of spying untested and untried.