It started with ardour and ended in bitterness, this affair which Simone de Beauvoir described as ‘the only truly passionate love in my life’. Documented in more than three hundred letters, her affair with the American writer Nelson Algren introduced her to the physical pleasure she had never found with Jean-Paul Sartre – and threatened to destabilise her carefully constructed writer’s life in Paris. Perhaps that is why, many years later, she repudiated the affair, insisting to a friend that ‘you have to make it clear that I lied in all those letters. Everything was a lie.’

Everything? When they met in February 1947, while de Beauvoir was on a lecture tour of America, they quickly plunged into an affair. Three months later, back in France, de Beauvoir was already addressing Algren in her almost daily letters as ‘my dearest husband’ and describing herself as his ‘wife