The Second World War had been won, but relationships between the Western allies and the Soviet Union were becoming increasingly strained, as the nuclear arms race made world peace precarious.
It was vital that Britain knew the Soviets' intentions and military capabilities, both offensive and defensive.
As a Military Attache in Sofia, and Commandant of an Intelligence Centre in the Balkans, it was SIS officer Colonel John Sanderson's job to find out. Sanderson handled agents who operated secretly behind the Iron Curtain at the height of the Cold War and organised hidden arms depots for stay-behind agents in case of a Red Army invasion.
Based on Sanderson's letters and personal accounts of his time with MI4 and MI6, we learn how he was sent to observe sessions of the Paris UNO Security Council in 1948 and to recruit emigres for infiltration behind the Iron Curtain, into Communist Bulgaria.
Fluent in French and Bulgarian, in 1949 Captain Sanderson was posted to Sofia as a Press Attache with diplomatic immunity, reporting on the Communist show trials.
Colonel Sanderson returned there twelve years later as the Military, Naval and Air Attache.
In 1961, having been tasked by London with photographing the latest MIG fighter, he was driven at night to Sofia airport's perimeter by a CIA colleague.
Closely followed by the Bulgarian secret police, he parachute-rolled, unobserved, out of the car with his camera.
Arrested at daylight, he escaped to the border and drove across Europe, still pursued by the ruthless Bulgarian Security Services. John Sanderson's early service life was equally challenging, from helping defend Britain's coastline in 1940, picking up shot-down pilots around Dover on a motorbike during the Battle of Britain, to fighting the Japanese in the Burmese and Indian jungles, before returning to London to join the Secret Intelligence Services.
In parallel with Sanderson's SIS career, living with Russian emigres in Paris, posted to SIS headquarters in the Berlin Olympic stadium, and later working together in the Intelligence Division of NATO headquarters Paris during the Cuban Missile Crisis, was his SIS friend RAF Squadron Leader John Aldwinckle, a veteran of SOE wartime operations in Halifax bombers.
All Aldwinckle's agents were betrayed by the traitor George Blake, as were all Sanderson's by Kim Philby. In John Sanderson's biography we get the detailed inside story of the Berlin Air Lift, the Suez Invasion, the Cuban Missile Crisis, and the fall of the Berlin Wall.
We see the results of Philby and Blake's treachery and the effects which the courageous actions of the two 'Olegs', the Russian Colonels Penkovsky and Gordievsky, had on the international politics of Khrushchev, Kennedy, Gorbachev, Thatcher and Reagan - and the consequences their decisions had for the course of world history. For over thirty years, John Sanderson worked for the British Secret Services - with his last mission, aged 74, as exciting as his first, being helicoptered into Sarajevo with an SAS team at the height of the Balkan War.