Norman Cohn wrote three great histories, each thematically related to the other. His first book, The Pursuit of the Millennium (1957), showed how apocalyptic beliefs fuelled medieval heresies and, in the 20th century, Nazi and Communist orthodoxies. His second, Warrant for Genocide (1967), exposed that arsenal for anti-Semites The Protocol of the Elders of Zion for the forgery that it was. His third, Europe's Inner Demons (1976), showed how the idea of the satanic pact was at the heart of the European witch-craze. In 1948 the great Annales scholar Lucien Febvre had written his (then) startling essay, "Witchcraft: nonsense or a mental revolution?" Cohn's published writings would provide the most satisfying answer to that question.

But first the nonsense had to be got out of the way. Not just the history – Nazi reliance on a dodgy document. But the historiography: credulous readers' reliance on Margaret Murray's fiction of witchcraft as Christianity's ancient religious rival. Cohn, the most modest and gentle of men, swept her 1921 romance The Witch-Cult in Western Europe into the dustbin. His weapons were, as in all his inquiries, patience, scrupulous testing of evidence and empathy into minds of very different cultures, all backed with formidable linguistic skills.

It was as a linguist, not a historian, that he had begun his academic career. The son of a Jewish father and a Catholic mother, Cohn had graduated from Christ Church, Oxford, with a First in Modern Languages. Wartime service in the Intelligence Corps may have reinforced his interest in the persecutors and the persecuted and ultimately in the ambition to write their history....