Stalin is the godfather of Islamic State. The Soviet leader died 60 years before the brutal fundamentalist caliphate began to take shape in Syria and neighbouring Iraq. But just as Stalin created a spy-state founded on fear, so the architects of Isis set out to forge a new caliphate using precisely the same methods.

Stalin’s USSR and the self-proclaimed theocracy ruled by Abu Bakr al-Baghdadi both laid claim to ideological purity; but both, in reality, were predicated on the acquisition of power by means of a fearsome internal espionage network.

The KGB, the East German Stasi and Saddam Hussein’s Mukhabarat intelligence agency are the direct progenitors of the Isis security apparatus. The proof lies in a cache of documents uncovered after a shootout last year