In 1927, the Anglo-Soviet relationship ruptured, and agent operations lay behind the break. One set of treasonous activities, those of the Macartney case, occurred within the context of several international incidents of considerable importance: the coup in Poland led by Marshal Jozef Piłsudski, the quickly following assassination of Soviet diplomat Pyotr Voikov in Warsaw, the Chinese civil war (including the Peking raid by British authorities), and more directly, the ARCOS raid of May 1927 and subsequent war scare. Viewed altogether, it is easy to understand why Wilfred F. R. Macartney’s attempt to give classified British military information to the Soviets struck British security and intelligence officers as being not only grave, but urgent, and why, too, they sought to arrest Macartney and his handler, German-born Soviet operative Georg Hansen, when the opportunity arose. Recent literature has highlighted risk-taking as a ‘quality essential’ to today’s intelligence operatives, but as the Macartney case shows, there is a fine line between risk-taking and bad judgement. The Macartney case also serves to highlight an early iteration of the ‘recruitment cycle’: spotting, assessing, developing, pitching, formalising, producing (handling) and terminating. Macartney’s history illuminates why he came to the attention of Soviet recruiters, what motivated him to spy, the particular characteristics that made him attractive to a Soviet recruiter, how he was spotted, and how he might have been assessed.

A second case, that of William Norman Ewer, concluded shortly after Macartney’s trial. The fact that Ewer, a Trinity College, Cambridge graduate who spied for the Soviets in the 1920s, was detected more rapidly than Kim Philby in the 1930s was due chiefly to his more primitive tradecraft. Under the cover of the Federated Press of America (FPA) and his job as foreign correspondent for the Daily Herald, Ewer ran a network of agents and informants that provided him – and the Soviets – with information from a number of government offices, some of which came from turned detectives in Scotland Yard. The Soviets and the CPGB, thus forewarned, were able to take appropriate action to protect their interests from counter-espionage operations. Revelations that Scotland Yard detectives had been compromised in the end worked in MI5’s favour. After years of deliberating on the appropriate division of labour among the intelligence services, in 1931 the SSC handed MI5 control of all British counter-subversion and counter-espionage – civilian and military.