This is especially true for Mark Strong who did not get even a single nomination anywhere for this performance. I can certainly understand why as Mark Strong is not a big name, which is always too much of an unfortunate requirement in the awards game, as well as this is an intensely subtle performance from Strong. I have to say it is a real shame that he went as unnoticed as he did, since this is quite an interesting against type performance from Strong. Strong usually plays fairly loud heavies, not that he does that badly. In fact he was quite enjoyable in The Guard as one, but usually the characters are almost prop like, such as his character in Syriana for example.
Strong shows a very different side to his acting abilities though as the spy Jim Prideaux, whose story is one of the most interesting parts of the film. I suppose I should say this will be spoilers filled, even though just by nominating him I sort of spoiled the film a bit, as the character of Prideaux appears to have been shot and killed at the beginning of the film. Prideaux is of course not killed and his testimony is one of the keys to Smiley uncovering the mole at the top of British intelligence. This is an extreme case of minimalism for Strong as his total amount of lines are fairly sparse, and most of them are at the beginning of the film when a meeting goes wrong.
The amount of lines he has matters not in fact it only helps with Strong's portrayal of the introverted Jim. Strong in this performance conveys so much with his face, and with a single look does more than some actors do in a single film. He almost creates his entire character on this aspect of the performance as it really does bring tremendous power within it. This is true whether it is a less stressful moment where Jim meets one of his students, an introvert like him, and through just the slightest smiles and welcoming eyes he shows the fact that Strong sees the boy as sort of a kindred spirit. The same goes though when we see Jim being tortured and Strong flawlessly portrays the sheer horror in Prideaux as well as his waning attempts to hold on to his secrets.
There is never a moment on screen that Strong fails to bring an honest emotional truth to his part of the proceedings, which stand as very important to the film. For the most part the men in the agency are either opportunist, or even they are not they are very cold like Control (John Hurt) and George Smiley (Gary Oldman), but there is the small group who, like Alec Leamus in The Spy Who Came in From Cold, are more deeply hurt by the tricks of the spy game. One of these is the hi man with a conscience Ricki Tarr (played well by Tom Hardy), and the other is Jim. Strong infuses a great devotion in Jim toward the service, as there he does not portray hating his time there, and seems to have regrets over having to give it up all together.
Strong though portrays an especially great pain within Jim over having to find the supposed Mole, and his sadness in finding out one of them is betraying the rest weighs on him greatly. Strong though even suggests that there may be more to this strain as perhaps Jim has created suspicions in his head. This is where his friendship, or perhaps more it technically speaking does not matter, with Colin Firth's Bill Haydon comes in. They actually only share one moment together, and fitting to Strong's performance they only share a look at one another, but that says it all. Although as absurd as it seems the two actors in that short moment establish the friendship, and amazingly conveys the deep connection the two have.
The fact that in the end of the film the mole in the organization turns out to be Bill leads to the two most powerful moments in the film brought about all due to Strong. The first being in his trailer at the school he teaches clearly wounded over the revelation, as well as embittered. Not one emotion suffices Strong as he portrays the intense internal struggle within Jim, as well still even has in the same moment he struggles to tell the boy to try to break his introversion, and not suffer from his fate. After this scene it leads to when Prideaux shoots Haydon in the most heartbreaking scene as the actors once again show the connection with one another, but Strong poignantly as well as silently brings to life both the hatred toward Bill over the betrayal, but as well as the sadness over the fact that he must kill the only person he has ever loved. This is a absolutely masterful performance by Strong, there is not a wasted moment or even a single facial gesture.