Nunca se afirmou qual é o seu nome verdadeiro ou o seu título oficial ou posição no aparato da inteligência russa.
Karla is a fictional character in several novels by John le Carré. A Soviet Intelligence officer, he most often appears as a distant antagonist of George Smiley. His real name is never revealed; instead he takes his codename from that of the first network that he recruited.
Quanto à sua importância para o enredo de Tinker, Tailor ..
Karla is first mentioned in Tinker Tailor Soldier Spy as the spymaster who recruited and controls "Gerald", the mysterious mole inside the Circus. By the time of that novel, Gerald has become Circus' number-two-man and Karla is using Gerald's handler, Alexei Polyakov, to deliver fabricated intelligence that appears highly valuable.
Karla appears briefly in the BBC adaptations of Tinker Tailor Soldier Spy and Smiley's People, though he does not speak in either. He is played by Patrick Stewart.
Karla appears briefly in the 2011 film adaptation of Tinker Tailor Soldier Spy as a voice, provided by Michael Sarne, as well as in a partial shot in a Budapest coffee shop holding Smiley's lighter.