Who is Roddy Martindale from Tinker, Tailor, Soldier, Spy and what is their importance?

Roddy Martindale is an employee at the Foreign Office. His job includes entertaining lesser foreign dignitaries. Martindale is not marries, and he worked for Whitehall for a short time.

Member of British Diplomatic service,as old as George Smiley, well versed in government gossip particularly as regards security services.First plants the notion in George Smiley's mind that all is not well at the Circus hinting that Alleline who is gaining influence,is not competent to run the service,and that he relies on a subordinate to build his success in raising the prestige of the Circus.The implication,evident in Martindale's demeanor as he fades into the night,is that something is rotten and a mole might be in effective charge of the service,and causing significant harm to the security of the nation.

Mick777, based on the miniseries at least, Roddy does indeed establish the dysfunctional status of the Circus, but not so much in Smiley's mind as in that of the viewer. Smiley is recruited by Lacan after Ricky Tarr alerts Lacan to the likely presence of a Soviet mole at the top levels of the Circus. Possibly the book uses Roddy differently though.