Late 1940s and 1950s

LATE 1940s AND 1950s

By 1948, the Soviets had undertaken systematic moves to bring central and eastern European countries under Communist control. These developments caused great concern in western Europe, as it was believed that the Soviets wished to expand their sphere of influence still further. As the then Attorney General Sir Hartley Shawcross put it on 13 March 1948, "the peoples of Western Europe ask themselves whose turn it will be next."

The British Prime Minster Clement Attlee announced on 16 March 1948 that Communists as well as Fascists were to be excluded from work deemed vital to the security of the State. Such individuals, Attlee declared, "would be prepared to endanger the security of the State in the interests of another Power."

A vetting system was established and the Service was given the task of supporting it. The measures undertaken following Attlee's announcement made a vital contribution to the safeguarding of national security. In a sense, this was not a new development; as far back as the First World War, the "preventive" security branches were at least as large and important as the counter-espionage branch. The provision of security coordination and advice is still a central part of the Service's work.

Internal reforms

The remit of the Security Service was reformed and clarified in 1952 by Winston Churchill, in his second term as Prime Minister. He delegated his personal responsibility for the Security Service to his Home Secretary, Sir David Maxwell-Fyfe. The tasks of the Service and the roles of the Director General were set out by Maxwell-Fyfe in a directive which provided the basis for the Service's work until 1989, when the Security Service Act placed it on a statutory footing for the first time (see "Statutory basis").

By the early 1950s, staff numbers had increased to about 850. This included some 40 Security Liaison Officers overseas, who provided advice and assistance to governments in the Commonwealth and Colonies.

Infiltration and subversion

The United Kingdom was a high-priority target for the Soviet intelligence services during the 1950s. It soon became apparent that the Soviets had already achieved notable successes in recruiting agents prior to the introduction of vetting.

In June 1951, two British diplomatic officials, Guy Burgess and Donald MacLean, abruptly disappeared from their posts. They reappeared in Moscow in 1956, where they announced that they had been Communists since the 1930s and had been supplying information to the Soviets since the start of the Second World War.

Klaus Fuchs, the British scientist who passed atomic bomb secrets to the Soviets

John Cairncross, a Secret Intelligence Service officer, was exposed as a Soviet agent in 1951. The 1950s also saw Klaus Fuchs's betrayal to the Soviets of the secrets of the atom bomb. The Security Service files on Fuchs were released to the National Archives in 2003.

The Service also kept a close watch on the activities of the Communist Party of Great Britain (CPGB). Various individuals associated with the Communist movement were monitored in the hope of uncovering any connections with espionage or subversive activity. A number of Service files relating to investigations of CPGB members have already been released to the National Archives, and we will be releasing further records in the future.

1960 to 1989 Ð'»

The Cambridge spy ring

The "Magnificent Five", as their controllers dubbed them, were a group of Soviet spies who were recruited at Cambridge University before the Second World War and subsequently obtained sensitive government posts. The five were Anthony Blunt, Guy Burgess, John Cairncross, Donald Maclean and Harold "Kim" Philby. They were among the most famous spies of the 20th century.

The existence of the spy ring came to light at the start of 1951, when Burgess and Maclean came under suspicion