Edward Gibbon did not enjoy his time at Oxford. Years after escaping the university, grim memories of its port-sozzled Anglicanism prompted him to float a celebrated counterfactual. Writing about the Battle of Poitiers, the great victory won by the Franks over the Arabs in 732, he pondered what the consequences might have been had the jihad into Europe succeeded. ‘Perhaps,’ he mused sardonically, ‘the interpretation of the Koran would now be taught in the schools of Oxford, and her pulpits might demonstrate to a circumcised people the sanctity and truth of the revelation of Mahomet.’

Today, as the city’s councillors ponder whether to permit the Islamic call to prayer to sound across the dreaming spires, Gibbon’s fantasy seems altogether less fantastical. Historians, their antennae twitching, have been duly quick to capitalise. David Levering Lewis, a Pulitzer Prize winner whose previous work focused on the nineteenth