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 was lucky, because Ewan McGregor had already been shooting with Roman Polanski for about a month before I got role. And he did a faultless impersonation of what it was going to be like. So when direction happened, it was like, "Oh yeah. That's what Ewan said was going to happen." And so it was a little bit less debilitating than it might have been.

When Roman Polanski did give you a "Great, great, great!" you were just like, "Thank you, Lord, for this magical moment."

Ewan McGregor and I said this to each other after we saw The Ghost Writer. Every time Roman Polanski did a "No, no, no!," he was right. It was really as if a sculptor was asked to sculpt the embodiment of despair - that was the attitude he would strike. But as with every sort of inspiring teacher you ever had who was strict and scary, when you get it right, the sun comes out, and it's worth it.

From a very young age, I wanted to get up on stage whenever I went to the theatre - the actors just seemed to be having so much fun. One of my worries about theatre, in fact, is that the actors are quite often having more fun than the audience.

For me, selfishly, The Postman didn't kill my career. It meant I didn't shoot straight and painfully into the limelight, but Rushmore came out of it. No one would have known where I was to cast me in Rushmore had I not been in The Postman. Because they shared a producer. Nor would I have been in The Sixth Sense. Nor would I be speaking to you now if Kevin Costner hadn't cast me in The Postman.

I had the best teacher in the business. Kevin Costner was my teacher. I was acting opposite him and he was directing me. The way he directed me, for which I am eternally grateful, is he would watch the scene back on the monitor, which is sort of considered unfashionable - you're not meant to watch yourself. But he was like, "Come around. Watch this. See there, you're doing a great reaction, but you're doing it out of frame." That was exactly what I needed. I learned how to act on film from him.