Few events have earned the dubious honour of being described as ‘the closest the world came to nuclear war’. The Cuban Missile Crisis of 1962 is one; the 1983 Able Archer war scare is another. The episode has produced a vast amount of literature, focusing on the US and Russian sides and, to a lesser extent, the British perspective. The episode has all the hallmarks of a great spy film: a paranoid, aging dictator in the Kremlin; a military exercise that almost ended in disaster; and a disillusioned spy providing intelligence that was pivotal in attempting to understand the complicated cycles of reaction and overreaction, perception and misperception.

On 2 November 1983 NATO forces began the latest in a series of scheduled military exercises. Able Archer-83 was a command post exercise designed to include senior officials from across the US government, the movement of 40,000 NATO troops, and hundreds of different missions. Importantly, it also included a component designed to simulate the release of ‘tactical’ nuclear weapons against a variety of Soviet and Warsaw Pact targets. From a Western perspective this was simply another in a regular series of war games and as far as the military was concerned, it ultimately passed off without incident and little more attention was paid to it.

That feeling did not last long, though, and there was some initial concern that the Russians had reacted in a peculiar and unconventional manner, particularly that the Soviet Air Force in East Germany had moved to a heightened state of alert. This fact had been noted but was not interpreted, initially at least, as being especially significant. What limited analysis there was at this stage suggested that the Soviet reaction could be attributed to the paranoia of the ailing Soviet leader, Yuri Andropov, in the Kremlin. This view would soon change, though.

As Andropov lay dying in a hospital bed in the last weeks of 1983 and start of 1984, his KGB rezident in London was busy providing snippets of high-value intelligence to the British Secret Intelligence Service. Oleg Gordievsky had volunteered to work for SIS whilst stationed in Copenhagen, Denmark, in 1974. He claimed to have become disenchanted with the Soviet system following the violent crushing of the 1968 uprising in Czechoslovakia.