It's great to have the chance to play a character before he goes to the dark side, or the yellow side if you will. Normally, you don't get that opportunity. The narrative of a movie usually demands that you are that guy from the start.

Part of me was fascinated by the idea that I would only get next week's episode a week in advance and wouldn't actually know where I was going with it, until the script landed on my mat. But, part of me wanted to know what was going to happen.

I've put my friends and family through the wringer over the years, I have to say, by doing unspeakable things to people, not the least of which was pulling out poor George Clooney's fingernails in Syriana.

And I think in your 40s, you land a little bit, physically and mentally, you arrive at a place where you feel you've learned some stuff. Having children at that point meant I had something very useful to do for the next 20 years.

In the movie, you have to decide as an actor how you are going to give a character presence. You can't really move, walk, and talk like yourself. This creates something so you have to find something "other".

My mother moved abroad when I was 11, my dad wasn't around from the time that I was a baby, so I was not the product of a family, but a product of observation - of watching what went on around me, of watching who I liked, what I didn't like, what I thought was good behaviour and what I thought was bad behaviour and tailoring myself accordingly.

I got sent the script [ Before I Go To Sleep] as usually happens and you have a little look. I know it's a bit of a cliché, but it was absolutely a page turner. I mean, I wanted to find out what happened next.