In the original screenplay for the film adaptation of Tinker Tailor Soldier Spy, Smiley muses that Control had once told him that Howard Staunton was the greatest chess master Britain had ever produced.
Control first appears in Le Carré's third book, The Spy Who Came in from the Cold, co-ordinating the simulated defection of Alec Leamas, a former West Berlin station chief who witnesses the killing of his source by Hans-Dieter Mundt.
Control next appears during The Looking Glass War, undermining The Department, a military intelligence directorate and rival to The Circus who are barely afloat and receive funding predominantly due to their research work.
Secretly, however, Control works with Smiley to orchestrate the downfall of The Department and sacrifice its agent, Fred Leiser, leaving him to be killed by the East Germans.
This lead to the capture of field agent Jim Prideaux, after which Control was forced to retire in disgrace, and Alleline became head of the Circus.
However, other characters such as Roddy Martindale claim Control is actually alive; that he faked his death at the shame of being "driven out" by Alleline and has been spotted in South Africa.
This originates from the initial used by Captain Sir Mansfield Smith-Cumming, RN, an early chief of the service, who signed his letters "C" in green ink.