Still, not everybody liked his choice. Some said he would have made a better point—to his compatriots, especially—if he had addressed the Muslim world from Indonesia, the country where (to quote a line from his speech) he first heard the call to prayer “at the break of dawn and the fall of dusk”. By speaking in Jakarta, Mr Obama might have challenged the mental association that (judging by polls) some Westerners still tend to make: Muslim equals Arab equals hostile to the West.

A new survey of the world’s Muslim population, by the Pew Research Center based in Washington, DC, will help those who are keen to break that link. It estimates the total number of Muslims in the world at 1.57 billion, or about 23% of a global population of 6.8 billion. Almost two-thirds of Muslims live in Asia, with Indonesia providing the biggest contingent (203m), followed by Pakistan (174m) and India (160m).

Perhaps more surprising will be the finding that the European country with the highest Muslim population is not France or Germany, but Russia, where 16.5m adherents of Islam make up nearly 12% of the total national population. Compared with other surveys, the report gives a lowish estimate for the number of Muslims in France (3.6m), as it does for the United States (2.5m); in both those countries, secular principles make it impossible to ask religious questions on a census.

Another set of data from Pew, albeit dating from last year, was at the heart of a report endorsed this week by two luminaries of inter-faith dialogue: Richard Chartres, the Anglican bishop of London, and Ali Gomaa, the grand mufti of Egypt.

In a change from the happy talk of many multi-faith exercises, the report grappled with some unpleasant trends: the rise, among Turks, of negative attitudes to Christians and Jews, and the rise in some European countries, like Spain, of anti-Muslim feeling. The fact that robed gentlemen are on good terms does not always lead to goodwill among their flocks.