What a disappointment A book as complex as Le Carré's can't be filmed without serious compression of the plot, but this mess wilfully makes unnecessary changes - look at the character of the Hon. Jerry Westerby, for example, as shown here and as written - and fails to explain some key elements of the plot. The result is that, having watched matters unwind slowly over two hours, we are suddenly led to what looks very much like Smiley having suddenly noticed something he should have seen before. There is absolutely no description of what the men at the top of the Circus do or of their pasts - Bland in particular seems to be paid for doing nothing very much - and some incidents that have lost their point because the story has been changed. One example is the befriending of the schoolboy Bill by a major character.
On the plus side, Mark Strong is convincing as Prideaux, and Gary Oldman does what he can with the part of George Smiley. Tom Hardy does a good job as Ricki Tarr, and David Dencik provides an interesting portrayal of Toby Esterhase. On the other hand, John Hurt plays John Hurt very well, and Toby Jones makes you wonder why anyone with half a brain would give Sir Percy Alleline any position of responsibility whatsoever. This is not the fault of the actors - they haven't been given much of a hand to play.
The film is atmospheric and, I suppose, is an interesting enough film in its own right, but it isn't the film of the book. Whether the book is, ultimately, filmable may be doubtful.