The most colourful explanation for the Italian exception is that Italy’s mafias have quietly deterred jihadists from gaining a toehold. The defect of that idea, says Arturo Varvelli of the Milan-based Institute for International Political Studies, a think-tank, is that Italy’s mobsters exert greater control in the south, whereas a sizeable majority of its Muslims live in the north.

“To some extent, it is the Mafia,” says a senior law-enforcement official. “But not in the way most people mean.” The fight against Italy’s formidably organised criminals has given its police a wealth of experience in monitoring tightly knit target groups. It was enhanced by the campaign to subdue the left- and right-wing terrorists who wrought havoc in Italy in the 1970s and 1980s. Organised crime and terrorism have also encouraged judges to take a more expansive attitude than in other European countries to issuing warrants for wiretaps and particularly to the electronic surveillance of suspects’ conversations. Italy’s recent history may also explain its hardline approach to apologists for terrorism.