I have many debates now with friends on the changes, and the continuing confusion over bringing up your children, instilling values, letting them make the right choices.

My parents' long and happy marriage was a great ideal to live up to, but a tough one.

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.

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.

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.

Family holidays and weekends are really brightly colored memories, full of my mother and father, rather than our nannies and au pairs.

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.