Britain learned of South African nuclear programme from USSR

Britain learned that apartheid South Africa was preparing to test an atomic bomb only after being alerted by the Russians.

Previously secret papers released at the National Archives show how James Callaghan, the Labour prime minister, was informed in August 1977 of a secret test site in the Kalahari Desert in a personal letter from Leonid Brezhnev, the Soviet president.

A Soviet spy satellite had discovered the site at Vastrap, in a remote area south of South Africa's border with Botswana, a week earlier. Two 750-foot shafts had been drilled in preparation for underground explosions. The Americans appear to have possessed similar satellite imagery but failed to inform their closest ally until after the Brezhnev letter.