Richard B. Spence, Trust No One: The Secret World Of Sidney Reilly; 2002, Feral House, ISBN 0-922915-79-2. a b c d "MI6 spies exposed by Balkan rivals". The Telegraph. 27 September 2004. Archived from the original on 10 January 2022.

By 2012, MI6 had reorganised after 9/11 and reshuffled its staff, opening new stations overseas, with Islamabad becoming the largest station. MI6's increase in funding was not as large as that for MI5, and it still struggled to recruit at the required rate; former members were rehired to help out. MI6 maintained intelligence coverage of suspects as they moved from the UK overseas, particularity to Pakistan. [73] The Irish angle is Donovan or ‘Red’ Grant, a Smersh killer, who in the movie is a blond powerful figure who goes round killing people at the drop of a hat, which of course is one of those myths about the Secret Service that people are always killing each other just like that, and that everyone has a ‘licence to kill’…Judd, Alan (1999). The quest for C: Sir Mansfield Cumming and the founding of the British Secret Service. London: HarperCollins, ISBN 0-00-255901-3. Consider the case of Colonel Dudley Wrangel Clarke, an expert in strategic deception, using a role as a war correspondent for the Times as cover. To extend his efforts, Clarke travelled to Spain where, shortly after arrival, he was arrested by the authorities dressed, "down to a brassiere", as a woman. Beaulieu". Pen & Sword Books. 20 January 2012. Archived from the original on 13 May 2013 . Retrieved 1 July 2012.

It is reasonably well known that the Zinoviev letter, which helped to bring down the first Labour government in 1924, has its forged origin in the Riga station of MI6. Less well known is the gallantry of the young naval officer, Lieutenant Agar, who broke through the defences of Kronstadt, sinking several Soviet ships in at attempt to extricate the MI6 agent in Russia, Paul Dukes, who eventually found his way home and had a long interview with Winston Churchill.Ian Cobain and Richard Norton-Taylor (18 April 2012). "Sins of colonialists lay concealed for decades in secret archive". The Guardian. London . Retrieved 25 June 2012. Dorril, Stephen (2002). MI6: Inside the Covert World of Her Majesty's Secret Intelligence Service. Simon and Schuster. p. 752. ISBN 9780743217781. Lashmar, Paul (14 May 1999). "The making of a traitor". The Independent. Archived from the original on 14 February 2019 . Retrieved 9 June 2013.