Roy Bland
In the fictional novel Tinker, Tailor, Soldier, Spy, Roy Bland is in charge of Eastern bloc spying for MI6 and known to Prideaux and Smiley by the codename 'Soldier'. He is suspected of being a mole inside 'The Circus' who has been selling top secret material to the Soviets.
Background
Roy is one of the poorer recruits of MI6 - Smiley and other high ranking officers are at least middle class (Bill Haydon is actually quite aristocratic). His father was engaged in manual labour of some kind and often violent towards his son - Roy memorably describes him as an "old Commie thug", and this forced Roy towards quite right wing materialist views. Nevertheless Roy was a highly motivated and intelligent person and managed to get a scholarship for a university degree (possibly Oxbridge). Smiley met him at St. Antony's College, Oxford, where he looks as though it has taken a lot out of him to get this far. It is not revealed whether he is a fellow of the college or not. Many have used this against him - Roddy Martindale snidely calls him the first "Red Brick Don to make The Circus (MI6)", which could refer to where he did his first degree, or the fact that St Antony's was founded comparatively recently (1950) and did not have as much prestige as other Oxford colleges.
At the time of Tinker, Tailor, Soldier, Spy Roy Bland had become head of Eastern bloc spying, playing a key role in "Witchcraft". He smokes a large quantity of cigarettes so frequently coughs and is out of breath. He is a loyal officer who helps brief Peter on the supposed threat that Ricky Tarr poses, and is shocked when the allegations AbOUT the mole are proved right and by the discovery it was Bill.