Tinker Tailor Soldier Spy (1974)

Some key points that are a bit hard to grasp, at least in some versions:

How did Bill Haydon know Jim Prideaux was going to Prague if it appears to be organized as a closely guarded secret by Control?
- the film suggests Prideaux must have told Haydon himself, his close friend, against Control's orders of secrecy, out of loyalty, and in order to protect his friend.
- The series suggests it was a honeypot
so which one is it?
How does Smiley deduce that the Witchcraft source, Merlin, is Poliakov? A key step is when top people at the Circus question him about Ricki Tarr, and appear to suggest that there is a link between Ricki Tarr and Merlin. And Ricki told Smiley that Poliakov as the link to the Mole. Smiley understands that it was Karla who tipped off London Center about Ricki's coming through Merlin. He also observers that Witchcraft gives ideological infiltration campaign intelligence after Ricki comes back, as a way to discredit Ricki. It is still all a bit indirect.

Tinker Tailor Soldier Spy character

1: Jim Prideaux captured. Some ex-colleague invites Smiley to dinner and keeps asking how incompetent people like Alleline climbed to the top of the Circus. Smiley recalled to service to meet Ricki Tarr.
2: Ricki Tarr tells his story to Smiley. Peter Guillam starts stealing material from the Circus, find missing page on the communication officer list. Smiley sets up his investigation operation.
3: Smiley meets Connie who tells that she was fired for suspecting Poliakov. Flashbacks show the ousting of Control and Smiley.
4: Guillam steals more material from the circus. While doing that, he is called by the top officers to inquire about Ricki Tarr being in England, which they suspect because they discovered that his family has come.
5: Jim Prideaux tells his story to Smiley, who cannot easily access the Circus reports about it. When he is returned to England, there was basically no debriefing, and Esterhase already knew about the Tinker Tailor codenames, presumably through Merlin.
6: Smiley hears the story of yet another ousted man, who heard the Russians knew in advance about Jim Prideaux' coming. Toby Esterhase dismissed him for alcoholism.

This is not bad, but some divergences to the better BBC miniseries, which presumably sticks more closely to the novel:

in the film Jim Prideaux is captured in a cafe in Prague, in the series it's in the woods. It is therefore much more plausible that he would have been shot.
in the film Peter Guillam is played by Benedict Cumberbatch, who feels a bit young to be Ricki Tarr's boss. Not impossible, but still.
the series is much less chronological, and more flashback based, as new information becomes available. The film is more chronological, which makes it easier to understand, but less interesting at the same time.
in the film they shoot the Russian girl Irina in front of Jim, in the series the fact that she was shot is only known through other sources. The film has more eye candy, which weakens it.
Toby Esterhase is not threatened in an airfield, only in a safe ;house in London.