By the end of World War II, weapons of war had developed far beyond anyone's imagination. Hitler had developed the deadly V1 and V2, which had devastated parts of London and elsewhere. The Allies knew that Germany was developing the atom bomb.

Strained relations between Stalin and the West meant that Britain and the US did not truly trust Stalin's intentions and worked to halt his aim of spreading Communism. For Britain and the US, it became a race against time to capture the German scientists in post-war Germany before the Russians took them back to the Soviet Union to develop the technology for themselves.

The main scientists were captured and brought back to Britain for six months, before being transferred to the USA to work on the Manhattan Project – which produced the first atomic bombs.

The nuclear threat was very real between 1945 and 1991, and at a number of points brought the world close to nuclear war.