On 13 March 1961 at the Old Bailey Lonsdale was charged with spying, along with associates Harry Houghton, Ethel Gee, and Morris and Lona Cohen (Peter and Helen Kroger) while the trial British authorities were still not sure of his true identity. In March 1961 defendants were found guilty, Lonsdale sentenced to 25 years. He was to start his sentence at Winson Green Prison, Birmingham. From his single cell he fraternised with some of the Great Train Robbers. In due course, the British and American security services managed to establish his true identity as Russian citizen Konon Molody.