It's All In George's Head

 Now, Johnboy has... let's call them archetypes, in his work. Perhaps "idiosyncratic personal tropes" is more accurate. The most important of these, I would argue, is an archetype I like to call The Man. Now, The Man is a character, but his relationship to the protagonist is also an aspect of the archetype. He is a limping dark eyed slender diminutive charismatic Byronic attractive sexually ambiguous promiscuous suffering-under-the-state ex-lutheran or atheist Jewish German true-believing zealous socialist, but he is also most importantly the protagonist's fraught friend-nemesis. Now, there are different levels of that: Sasha is Teddy's friend who is also kind of a dick and keeps dragging Teddy into dumbass bullshit; Karla is George's nemesis who intentionally ruined his marriage and polluted the Circus and who George is obsessed with in a way that can sometimes reasonably qualify as hatred, at least in Smiley's People.

I would consider Axel H. in A Perfect Spy to be the most accurate depiction of the archetype of The Man, and I generally consider him to be the basic template which all other iterations deviate from. He was written later than most other iterations, true, but the combination of 1) the fact that he carries the most "The Man" archetypal traits of any of them, 2) the fact that his arc seems to kind of be what the others were portraying with the details changed, and 3) most importantly, the heavy autobiographicality of A Perfect Spy, cause me to still consider him to be the template.

Among other things, taking Axel as the template helps to explain Smiley's relationship with Karla.

( Spoilers for both APS and the Karla Trilogy ahead )