Hellish Nell: Last of Britain's Witches (rev. Ed.), by Malcolm Gaskill

From the publisher's website: 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.

Further information at the publisher's website: Penguin