One of the last criminal trials using the 1735 Witchcraft Act was, improbably, in London in 1944. The accused was Helen Duncan, a middle-aged Scotswoman. This is her extraordinary story.

Helen Duncan - known since childhood as 'Hellish Nell', for her uncontainable nature - was one of the most popular mediums of the twentieth century, holding seances around the country where she was believed to manifest the spirits of the dead. What happens when we die? It was the question of the age for a generation which had endured one world war and now was living through another. Mrs Duncan's seances offered an answer.

But when she started foretelling naval disasters, she also attracted the unwelcome attention of the secret service. And so just weeks before the Normandy landings, absurdly, anachronistically, she was prosecuted for witchcraft and jailed. Was Nell a conjurer, a martyr or a security risk? Hellish Nell was first published in 2001 to widespread acclaim.

It remains in this revised edition a fascinating window into the unsettled spiritual and psychological mood of the times: a sensational tale of spectacle, credulity and cruelty, and of Britain's last witch.