I had this extraordinarily bizarre moment when, two Fridays ago, my missus gave birth to our second child at 11am and by the same time the following day I was sitting around a table with Ridley Scott, Russell Crowe and Leonardo DiCaprio in Rabat in Morocco, rehearsing a scene we were going to shoot the next day.

When you're making a psychological thriller, what you need to do is have an audience on shifting sand so they're never quite sure where they are.

Interestingly, this character [Doctor Nash] is probably closer to me than somebody like the evil Sir Godfrey in Robin Hood or Lord Blackwood who wants to take over the world in Sherlock Holmes. This is a character that's English, he's based in London, and so it's closer to me than a lot of stuff I've been doing recently.

I'm very organized and tidy in my home life and I generally do something myself rather than farm it out to somebody else. I don't have an assistant or anything because I think I can do it myself.

Rowan Joffe was on top of everything. He knew exactly how he wanted everything to be, right down to the fact when I made those telephone calls, I didn't do it afterwards in a studio. I think that's how he operates. He likes it to be as real and as clear as possible.

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.

I just invited close friends and family, the usual suspects whose opinion I value but who I know will enjoy the film [Before I Go To Sleep]. I don't know how difficult it is for them to suspend their disbelief because they obviously know me and what they're seeing is not me.