Josephine Baker: New light on how dancer-turned-spy fought the Nazis

She was, according to the US wartime counter-intelligence officer Lt Paul Jensen, "our No 1 contact in French Morocco", supporting the allied mission "at great risk to her own life - and I mean that literally. We would have been quite helpless without her."

- Jon Henley

Donald Darling, a British intelligence agent, had her down as a "cherished agent of [Charles] de Gaulle's government". The UK foreign intelligence service MI6 called her "the pet lady agent" of the Free French.

Before the second world war, Josephine Baker had been "the black Venus": the world's first female superstar of colour, dancing the Charleston dressed in nothing but pearls and a banana skirt, parading her pet cheetah, scandalising and delighting le tout-Paris. After the war, she became a US civil rights campaigner, speaking with Martin Luther King Jr at the 1963 march on Washington and adopting 12 children from eight countries to live with her in her chateau in the Dordogne, south-west France.

During it, she was a spy. Recounted, often unreliably, in the memoirs of people (including Baker) with a story to spin, the entertainer's wartime exploits have long been a subject for mythmaking.

A new account, working from contemporary, often unused sources, has uncovered evidence that Baker was a highly effective agent who used the same celebrity that provided the cover for her espionage as a powerful means to promote the cause of equal rights.

"Looking at her life through the prism of the war really helps us understand who she was and to make sense of what she did later on," said Hanna Diamond, a professor of French history at Cardiff University and the author of Josephine Baker's Secret War, which is published tomorrow.

"The war was so important; it's the missing piece of her puzzle. She [Baker] was amazingly well equipped to be a spy: a performer, through and through. Her motivation came from the huge debt she felt to France, which had made her a star and it had its roots in the racism she grew up with."