Usually the casting process is lengthy and humiliating, but in this instance, The Ghost Writer, it was just too easy. I was sitting in a rental car on an L.A. street and my cell phone rang, and it was Roman Polanski on the line. I couldn't really believe my luck. He said, "See you in Berlin." I sat staring at a palm tree, thinking how surreal that was.

I wanted to play a TV detective because it's a rite of passage; I wanted to experience every area of acting. I haven't done comedy or as much Shakespeare as I had intended.

We had an ancient Russian acting coach at my drama school who said the worst offense you could commit was to let your subtext show. That is the point of acting, is to be saying one thing and not be allowed by society or your predicament to show what you're really feeling. In a way, I think that's why the therapy generation has killed script writing, because all you ever get is people going, "Hi, I'm feeling really angry right now."

Carey Mulligan is completely self-possessed. She knows what she's doing, and again, quite like the big-hitters I was talking about, my job was just to feel and reflect back the amazing performance coming my way. If anything, I was slightly pathetically flying in her tailwind. She's an extraordinary actress.

I don't tend to spend the whole day in the personality of the person I'm playing.

I guess maybe I was hired to play in the Doll House because of my dinner scene in The Sixth Sense, which has been scrutinized a thousand times as to whether you know Bruce Willis is dead, or whether I'm talking to myself. I think that maybe if that could be my forte, to do a scene and be able to say it could be read this way or that way.

Ewan McGregor is a very genial and entertaining man, and Pierce Brosnan is possibly the nicest man in the world. Actually, it was quite a genial set The Ghost Writer, but the weather and the colors and the actual surroundings were oppressive. But it was a created atmosphere. What was so striking is that Roman Polanski had his crew from The Pianist, and we were shooting in Berlin, so there were German and Polish and French people, and I was just sort of enjoying being in this mix of people, all kind of rubbing along together. That felt good.