The myth that the CPGB was an independent political organization free of the Kremlin’s control was dispelled through surveillance and penetration conducted by MI5 from the party’s creation in 1920 to its dissolution in 1991. The CPGB’s external radio communications with Moscow were intercepted and read between 1934 and 1937, and the resulting decrypts, code-named MASK, demonstrated that the party was effectively controlled by the Comintern and revealed the existence of underground cells operated under a rigid discipline enforced by a Control Commission. Penetration by MI5’s mole Olga Gray resulted in the conviction in January 1938 of the party’s national organizer, Percy Glading, on espionage charges.
During World War II the CPGB was obliged to reverse its policy of opposing a “capitalists’ war” when the Ribbentrop-Molotov pact collapsed with the Nazi invasion of the Soviet Union, but the Soviets continued to develop espionage networks in Great Britain with the CPGB’s assistance. In 1941 Oliver Green gave MI5 an account of an undiscovered spy ring based on volunteers recruited during the Spanish Civil War, and in 1943 the CPGB’s national organizer, Douglas Springhall, was convicted of receiving classified information from an
Air Ministry employee, Olive Sheehan, and from a Special Operations Executive officer, Capt. Ormond Uren.
The NKVD regarded the CPGB, like other Communist parties, as a useful operational surrogate, and activists such as James Klugmann (later the CPGB’s official historian) and Bob Stewart were harnessed to act in various capacities, including couriers, talent spotters, and recruiters.
During the postwar era, Moscow sought to disassociate the CPGB from involvement in espionage, although two of the most serious prosecutions—of ideological spies Allan Nunn May and Klaus Fuchs—implicated the party. Similarly, all the Cambridge Five spies were found to have had covert CPGB links in the past. After the end of the Cold War, Russian intelligence continued to exploit its CPGB links, as evidenced by the conviction of Michael Smith, a defense contractor who was entrapped in a sting operation after he had been
identified by a KGB defector, Col. Viktor Oschenko, as having been an important source of scientific and technical information from Thorn-EMI. Smith was arrested in August 1992 following an MI5 false-flag operation. He admitted selling details of the fuse for the We.177 nuclear bomb and was sentenced to 25 years’ imprisonment.