I apologize if these questions have been answered in other threads...I couldn't find them, and it's been a LONG time since I read the book.
Does Smiley know who killed Haydon? He acts as though he doesn't, but he's too smart not to know.
Why does Ricki pull the gun when sending the message in Paris? Could he not have sent the message otherwise?
It really seems unlikely that Smiley doesn't know. In the book, it's pretty clear that Guillam knows. Neither does anything about it, probably reasoning that it wouldn't do any kind of good.
Ricki needs to get his message into the hands of Gerald--who we know at this point is a member of the Witchcraft committee and one of the top 3 at the Circus--and the only reliable way of doing that is to send it via the Circus' own communication infrastructure. Any other method risks having the message intercepted by Gerald before the other two can become aware of it.
Regarding Ricki Tarr and the gun in the scene at the Paris Station:
I'm torn between two explanations,
1.) Ricki needed to use the threat of force to make the staff send his message.
2.) He was just doing some macho posturing, to smooth over the fact that he was really the one under the gun.
A combination of the two is certainly possible.
I read the original query at between 2 & 3 in the morning and thought, “I don’t understand this question. Sleep on it and see what the others think.” Now I am beginning to see the light. But this is one of the fascinating things about the story. You think you understand the plot, and then some quirky detail jumps out and stumps* you.
* American readers may not understand this cricketing analogy!
Smiley is surely convinced that Prideaux killed Haydon. He perfectly knows what Prideaux is good at (so did Haydon 'Good to se that have not lot your touch'). But how to prove it - and why should he try?
Ricki Tarr is a wanted man inside the SIS - there's price on his head so he has to use coercion - and a 9 mm Browning (or whatever the gun is) is very convincing!
It's a pre-war Beretta (Model 1934 or '35) same as the handgun Tar uses earlier in the series and the same as that which Smiley loads and primes (aka "just fiddling") whilst on the 'phone to Mendel in the last episode.
Remember what the goldfish said? "There must be a God, I mean: who changes the water?"
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