He is the subject of the biography Agent Jack (2018) by Robert Hutton,[5] and his adventures were the inspiration for the novel Our Friends In Berlin by Anthony Quinn[6] and for a major character in the novel Transcription by Kate Atkinson.
"[14] By 1942, Roberts was posing as a German Gestapo agent named "Jack King", a member of the Einsatzgruppe London, to obtain information about Nazi sympathisers in the UK.
As Jack King, he was in direct contact with six men and women who believed he was working for the Germans, and gave him information on "scores and probably hundreds" of Nazi sympathisers in the UK.
[15] Originally his mission was to infiltrate Siemens-Schuckert (GB) Ltd, the suspect British arm of the German company, until he met a "crafty and dangerous woman" named Marita Perigoe.
[16] According to Roberts, writing in his reports back to MI5, some of the fifth column fascists he dealt with had such hatred for Britain, driven by anti-semitism and the propaganda of Mosley’s group, that they "applauded" women and children being killed by German bombs.
[18] In 1947, Roberts was seconded to the Secret Intelligence Service (MI6) to work in Vienna, posing as a British civil servant and passing information to a Soviet agent, Jellinek.
[9] After the Cambridge spy ring, a group of double agents including Guy Burgess, Donald Maclean and Kim Philby, were discovered by MI5, Roberts, who was then in Canada, was visited by Barry Russell Jones of MI5, who asked him about any suspicions he might have about his former colleagues.
[18] In a 14-page letter sent in 1969 to Harry Lee of MI5, Roberts wrote of his anxiety and frustration about his time in the service, and stated that he believed he had been followed and spied on by agents in London.
[13] He then lived in Nettlestone on the Isle of Wight before emigrating to Canada,[19][5] where he eventually settled in Ganges, Salt Spring Island, British Columbia.
[20] He died on 17[1] or 18[2] December 1972, leaving a widow Audrey, two sons (Maxwell, born 17 January 1936, and Peter), a daughter (Crista McDonald), three grandchildren and two sisters.