Tinker, Tailor, Solider, Spy was a triumph. Masterfully adapted, perfectly cast and exquisitely shot. But I can't have been the only person looking at their watch half way through. Because, to be honest, it was baffling.

The film had been ingeniously edited so that most of the important stuff was missing. As a result, you spent the whole time trying to fill in the gaps between scenes. This took you straight into the mind of George Smiley, who spends his life looking for what is hidden.

But unfortunately, Smiley's mind is not a nice place to be. The man is paranoid. So as the film goes on you feel more and more humourless, suspicious and emotionally suffocated.

I left the cinema certain of two things. First, that I was not suited to a life in the secret services. Second, that Tinker, Tailor, Soldier, Spy was not suited to the big screen.

But what about the pitch-perfect performances? What about the achingly realistic 1970s setting? What about Gary Oldman's glasses? But none of these matter. Because the problem with Tinker, Tailor, Solider, Spy goes deeper than that.

In truth, the story is just too complicated for cinema. Mental exercise like that belongs in a book. Or maybe a Sudoku. When you go to the cinema, or the theatre, or even a concert, you are not in control of the tempo. You cannot pause what you are watching. You cannot go back over stuff. You are at the mercy of the director, and whatever deadline he is keeping to.

Some things fit that format, such as jokes, ghost stories, and fighting. But something intricately constructed and emotionally ambiguous is just too demanding. And what is more, cinema should never let you doubt who the baddie is.

In Martin Amis's The Pregnant Widow his protagonist comes out with this zinger:

"Pride and Prejudice, Keith could have said, had but a single flaw: the absence, towards the close, of a forty page sex scene."

I couldn't help feeling the same thing about Tinker, Tailor, Soldier, Spy. What was missing was a good thirty minute car chase slap bang in the middle. With machine guns. And maybe even a tank.

This is not to say that it was a bad piece of art. Just that it wasn't very enjoyable. No doubt spying throws up lots of interesting ethical issues. But next time, if the choice is between a laborious exploration into the morality of espionage, and the Bourne Ultimatum, I know which one I will go for.