An attempt that to me, as a long standing fan of John Le Carre's Smiley trilogy, consistently hits false notes despite the well known names in the cast.

Rating: Null/10 (29 July 2016)

This movie has some good aspects to it, as one would expect considering the budget and the cast. Unfortunately those are overshadowed by a lack of understanding of the characters and the book(s). None of the characters ever felt either real or true. Which is so very different from the books where all the characters feel very real indeed, even if we may not always understand them. Colin Firth as Bill Haydon is the only main character that I feel somewhat channel the true personality of his persona.
This may partly be casting but is probably mostly the directing. The choice to make Peter Guillam gay is a particular jarring; instead of this very down to earth physical ladies man with a never ending boyish charm, which is not only an essential part of his persona but also key to how he gets along and obtain information, Peter is a stiff suit with a personal crises when he has to break up with his bf. As if there isn't enough ground to cover storywise wo inserting a PC sideline which also confuses the main storyline bc it does not fit.
You are better off watching the BBC mini series from 1979 starring Alec Guiness. Or if you haven't: read the Smiley trilogy. For a softer start, begin with The Spy Who Came in from the Cold. It will surprise you :-).