PM warned of Soviet `A-bomb kit'

Clement Attlee was warned by defence chiefs to be on alert for Russian agents arriving with suitcases full of kits to make an atomic bomb to blow up London, according to top secret documents newly cleared by the Cabinet Office.

The warning reached the Labour prime minister in July 1951 as the Cold War intensified. A secret file, codenamed "Tube Alloys", reveals that Sir Norman Brook, the Cabinet Secretary, sent Attlee a memorandum outlining fears that a bomb to wipe out London could be put together in a garage.

"The chiefs of staff have been considering the possibility that the enemy [the Soviet Union] might open the next war with an atomic attack on London on the model of the Japanese attack on Pearl Harbour - without warning and without any formal declaration of hostilities." Most likely, they would try to drop their bomb from an aircraft, the thinking went, but probably even in peacetime a hostile aircraft could be intercepted and driven off, and the memorandum warns that a clandestine attack might be made.

"An atomic bomb might be broken down into a number of parts and introduced into this country in about 50 small packages of moderate weight. None of these packages could be detected by instruments as containing anything dangerous or explosive, and even visual inspection of the contents would not make identification certain."

The packages might be brought in as ordinary goods from Russian ships, or even in diplomatic bags. "The bomb could subsequently be assembled in any premises with the sort of equipment usual in small garages provided that a small team of skilled fitters was available," Attlee was warned.

The documents were found at the Public Record Office by Professor Peter Hennessy of Queen Mary and Westfield College, London University, and will form part of the annual Attlee Foundation lecture he is giving at the college tonight.

They had been released by 10 Downing Street, under the Waldegrave initiative in which classified Cold War files are all being reassessed.

The advice to Attlee warns there would be problems if officials tried to screen all Soviet diplomatic bags, and it recommends stepping up surveillance of the Russian embassy in Kensington to monitor any suspicious lorry movements.

Attlee does not seem to have been unduly concerned. He agreed to discuss precautions with ministers, but by the time they were all back at their desks after the summer recess, an election had been called. Labour lost, and the file was closed.