The vizier’s son was called Nasr al-Din. He and his father, known as Abbas, had good reason to run. Behind them they left Cairo spattered in blood. Days earlier the two men had successfully conspired to kill the Fatimid caliph, al-Zafir, as revenge for his attempt to remove Abbas from his post. The assassination had triggered the violent deaths of several of the caliph’s brothers, a steward of the royal household, at least one manservant and a substantial number of Egyptian soldiers.

