The Anglo-Soviet Trade Agreement of 1921 did not put an end to Bolshevik activities in Britain. It did not dampen Soviet propaganda, attempts to meddle in British domestic affairs, or the British fear of their doing so. Indeed, concerns that the Soviets were attempting to influence British unions and workers led to a political crisis and influenced Parliament’s decision not to ratify a second trade pact, which the two nations had negotiated in 1924. It also led Parliament to vote no confidence in the still new Labour government barely after it had gained power for the first time.

Earlier that year, Prime Minister Ramsay Macdonald had formally recognised the Soviet Union, the first in a series of events that led to his party’s ouster in October. In the autumn, when the government dropped its prosecution of the communist John Ross Campbell, who had been accused of encouraging revolutionary action, Parliament’s passed a resolution of no confidence in Macdonald. The third general election in less than two years was called for the end of October.

It was then that SIS supposedly intercepted a letter ostensibly written to the CPBG by Grigori Zinoviev, the head of the Comintern. The missive urged the mobilisation of labour and indicated that the Russian trade delegation, in the midst of renegotiating the terms of the trade agreement, would provide the necessary funding. The letter, almost certainly a forgery, was published on the eve of the general election. To some, it provided yet more evidence that the Labour Government was ill equipped to confront communist subversion, and Baldwin campaigned on the dangers of socialism. Nonetheless, Labour gained million votes in the October 1924 election but was unable to surmount the Tories’ landslide victory, gained mainly on the back of the Liberal vote’s collapse.

Unrest characterised British intelligence as well as politics, and inter-service tensions again found a forum in the reconstituted SSC. As organised labour came together and appeared increasingly potent, the government sought tighter coordination and more efficiency in British intelligence. Prompted by the Zinoviev letter, ‘Quex’ Sinclair used the 1925 SSC to try to put himself at the head of an amalgamated intelligence branch – a suggestion that stirred considerable dissent from the heads of other services.