A Dandy In Aspic (1968)

Thirty-six year old Krasnevin is a KGB agent who has lived his entire adult life, hence his entire career, in Britain undetected by the British as a foreign agent. It is only part way through that career that he has acted as a double agent under the pseudonym Alexander Eberlin working for the British secret service. In being the assassin of a string of three British agents working the same file, Krasnevin is beginning to feel burnt out, longing to get out of this double life and wanting to return permanently to the Soviet Union, his request denied by his superiors who believe even in his burnt out state that he is of more use to them in Britain. But with those assassinations, "Eberlin" is assigned a new mission by his British superiors in partnership with an agent named Gatiss, the latest to fill the position of the murdered agents: to find and kill the Soviet assassin, who they only know by his name, Krasnevin. With his life on the line with his predecessors assassinated, Gatiss trusts no one, least of all Eberlin who many within the service already dislike in his apparent arrogance. The Brits further believe that the assassin is a double agent, but one currently in West Berlin. As he and always suspicious Gatiss move their base of operation to West Berlin, Krasnevin/Eberlin has to figure out how best to handle the situation, he coming to the realization that the Soviets themselves may find him dispensable if he is no longer of use to them. Complicating matters further for him is the presence of beautiful British socialite, professional photographer Caroline Hetherington, who seems to be around a little too frequently for her not to be part of a conspiracy against him.