On a hot autumn evening forty-five years ago, two spies, one from the KGB, the other from MI6, sat drinking vodka in the small bathroom of a house in the semi-abandoned compound of the British embassy in Tehran. The Russian, a very tall man, perched unsteadily on a laundry basket, while the Englishman sat on the toilet. Foreigners in Iran were closely monitored, so there was the strong possibility that the house was bugged. To cover the sounds of their voices they left a radio playing and turned on the cold taps in the bath and the handbasin.

The KGB officer, Vladimir Andreevich Kuzichkin, knew of a plan which could have changed the course of the Cold War – a plan which, if enacted, might have led to a superpower confrontation and even nuclear war. He was offering to share his secrets with his Western counterpart. But in exchange he wanted help with a personal problem.

The plan was for a coup by Soviet-backed Iranian communists, supported by a Russian invasion. It was 1981 and the Iranian Revolution was young, the theocratic regime still unstable. For the time being it had the support of the well-established Communist Party or Tudeh (Party of the Masses); but the