Eight centuries ago in Turkey, at a gathering of intellectuals, a Muslim sultan insisted that one of his courtiers write a book about an unlikely subject: thieves and con artists. The sultan, Rukn al-Din, had secured another such book from Spain, but he wondered: ‘What’s left out of it?’ The set-upon courtier was Jamal al-Din Abd al-Rahim al-Jawbari, and the commissioned Arabic work, Kashf al-asrar (Exposing Secrets), his only surviving text. But why would a powerful ruler such as Rukn al-Din, presumably safe from street-level scammers, order a guidebook about the medieval Islamic underworld? The answer is most likely nostalgie de la boue — a way, as Tom Wolfe was to argue in Radical Chic, to assert superiority over the ‘middle-class striver’s obsession with propriety and keeping up appearances’.