The contrast between the leafy suburbs of Hampstead and industrial Woolwich on the southern side of the Thames could not be greater. What they shared in the 1930s, however, was a central role in the history of Soviet espionage in this country. In Hampstead the spies lived together in the Lawn Road flats and in the neighbouring streets; whereas in Woolwich they worked alongside one another in the less salubrious – albeit more palatial – engineering sheds of the Woolwich Arsenal, a munitions factory built in 1641 and sprawling over some 1300 acres. The Hampstead and Woolwich spies, however, could not have been more different. While the spies in Lawn Road were university-educated Austro-Hungarians, working in London for the Third Section of the Fourth Department, the Woolwich spies were English and working class. The ringleader of the Woolwich spies was a former member of the CPGB's Executive Committee, Percy Glading, who had been dismissed from his employment as an Examiner in the Naval Ordnance Department at the Woolwich Arsenal in 1928 for holding communist beliefs His sacking was quite abrupt:

Glading refused, and in a subsequent statement to the Arsenal authorities questioned the practice of testing Arsenal workers for ‘political fitness’:

Glading's dismissal from the Arsenal – solely on the grounds of Communist Party membership – played no small part in his decision to spy for the NKVD. In October 1929, after a six-month period of employment at a private engineering firm in East London, he travelled to Moscow to study at the Lenin School using the pseudonym, James Brownlie. He returned to London in April 1930 and there he was employed in the Colonial Department of the Communist Party until August 1930. Between May 1931 and March 1937 he worked as the Assistant Secretary for the League against Imperialism (L.A.I.).