The image of Karla (spoilers)
SPOILERS....I think it's great that the two times we actually see the feared and dreaded master adversary Karla in TTSP and SP, underplayed by the masterful Patrick Stewart, he's looks like a caged animal, under arrest by British Intellegence. He says not a word during both encounters with Smiley. It's his eyes that do all the talking.
What a build-up by leCarre to this otherwise unseen and terrifying entity! When others talk of "The Sandman," they tremble. His long "ears," his global reach and his lethal "solutions" to all unwanted meddlers who got into his Great Game were made quite evident by many who knew of him and the long string of corpses left in his wake around the world.
The mythos of Karla is hard to reconcile with the fleeting physical appearance of the great adversary of "Control" and George Smiley. Just as leCarre intended...
CmdrCody