Who is Aleksey Polyakov from Tinker, Tailor, Soldier, Spy and what is their importance?

Colonel Gregor Viktorov, also known as Aleksey Polyakov, is a Soviet agent. He graduated from Leningrad State University, and his cover at the Russian embassy in London was as a cultural attaché. Polyakov lived in Highgate and was in charge of briefing and debriefing the mole. His identity is revealed when Ricky Tarr informs the British of his true identity.