Right-wing extremists (KV 2/1505-1524) George McMahon (KV 2/1505-1506) George McMahon was an Irish fantasist who was involved in a far-fetched plot to assassinate Edward VIII in 1936 and tried to provide dubious information about Italian and Irish Republican plots to the authorities before himself embarking on a career of producing anti-Semitic propaganda.
KV 2/1505 covers 1933-1945, and begins with letters from McMahon to the Daily Worker being intercepted. The file has been weeded so the content of the letters is no longer available, but McMahon soon came to the Security Service's attention again in 1935 when he approached Special Branch with details of a supposed plot to ship arms to the Irish Free State. The following year he provided information about the intelligence role and activities of Italian agents in the London embassy, some of which turned out to be true, though most were inaccurate. His next approach came on 14 July 1936 when he provided details of a supposed Communist plot to assassinate the King. He was ignored, and two days later McMahon himself threw a loaded revolver at the King as he passed a crowd during a parade, and was arrested. (The Metropolitan Police file about this incident - MEPO 3/1713 - was released in January 2003.)
The Security Service report on the case to Sir Russell Scott is on the file, along with correspondence with the Director of Public Prosecutions about the conduct of the case. McMahon was subsequently sentenced to 12 months' hard labour, but after his release he was soon drawing attention to himself again. In a letter of November 1939 he claimed to have had a lengthy personal meeting the previous year with senior Nazi Julius Streicher, and to have information to offer. Worse followed, when in 1940 he began sending violently anti-Semitic letters mocked up on War Office letterheads purporting to be official communications (examples, including a virulent attack on Hoare-Belisha, are on file).
The Security Service continued to observe McMahon through 1945-1951 (KV 2/1506), and letters from McMahon to Oswald Mosley are amongst those intercepted pieces of correspondence on file. A rather weary minute sums up McMahon thus: "...he is the sort of man who is perpetually thinking out magnificent schemes but who has very little ability to execute them..."