As barrister in 1911 he had successfully defended the anarchists Yourka Dubof and Jacob Peters who were allegedly involved in the Sidney Street siege (also known as the Houndsditch murders) which so embarrassed Winston Churchill. According to Donald Rumbelow's "The Siege of Sidney Street", Peters was guilty but the prosecution's case was a shambles. Peters later returned to Russia to play a leading part in the Bolshevik revolution; he became deputy director of the Cheka and worked with Lenin and Dzerzhinsky.