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.

I'm not a writer, inherently. Most of the writers I've met have stories they need to tell. I don't have that. I'm an interpreter. I like getting a script, seeing a character and thinking, "Oh, wow, I know what I can do with that."

I loved making The Imitation Game and it's really gratifying to hear the audience's response to the character that I play. It was just a little thing that I did because I really liked the film and I liked Benedict [Cumberbatch] and I loved Morten's [director Morten Tyldum] previous film, Headhunters. For me, it was something I did thinking, "Wow, this is a lovely quality piece of work."

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 sure part of the baggage that I bring having played a lot of villains is also pertinent to the movie [Before I Go To Sleep], because I'm sure people look at me and think, "Oh, I'm not sure I trust him or not."

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 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.