Jansen has no illusions that researchers will ever discover the real, historical Mohammed. The source material is too fragmentary. In his account he takes as his starting point an Arabic biography written by Ibn Ishaaq in the mid-eighth century, around 120 years after the presumed date of Mohammed’s death. Jansen shows how this biography, like other old Arabic biographies, is full of fabrications. He wonders how generations of Western experts were able to follow the example of orthodox Muslims in accepting Ibn Ishaaq as a reliable source.

The fantasy Mohammed of legend has lost none of his importance over the centuries and many Muslims still regard him as an infallible example. For them the biographies are historically accurate and they believe it is possible to deduce from them how they must follow the prophet. This is dangerous, Jansen argues, since the biographies are marked by a bloodlust that is contagious even after fourteen centuries. The prophet commits many mass murders, particularly of Jews. Cynicism is rife. ‘Keep that she-devil away from me,’ exclaims Mohammed as a Jewish woman weeps at the sight of the bodies of Jewish men at the Khaybar oasis, where he also has a man tortured to death.

For extremist Muslims these ancient stories convey commands that are as valid today as ever. Jansen suggests that the murder of filmmaker Theo van Gogh in 2004, for example, perfectly fits the pattern of assassination of those who mock, regularly ordered by the prophet. A close acquaintance of Van Gogh, Jansen is a formidable participant in the current debate surrounding Islam in The Netherlands and he denounces attempts by colleagues in the field to gloss over uglier aspects of the faith, one such being the acclaimed Scottish academic William Montgomery Watt.

In The Historical Mohammed Jansen tries to remain charitable, even funny, but the underlying tone is sombre. The dazzling narratives and sometimes delightful jokes are outweighed by horror stories.