I felt, you know, body and soul, as it were. But, of course, I mean, I - at that age, I didn't think in terms of being professional. I didn't know anything about it. That happened later.

It's quite interesting, looking back at the first one [film about Harry Potter], nobody knew whether or not it was going to be successful as a film. The books were of course already very successful, but that's happened before, where the books were successful and the films weren't at all. But it turned out that they were.

I think I'd rather do [acting] in the real place. It requires different things, working with green screen, but its an imaginative exercise anyway, the whole business of acting, so it just gives you a bit more to feed the imagination. Unless it's really silly, just two of you stuck in a space with nothing but green screen that's got to be pretty difficult.

A mathematician either has a feeling for equations and an understanding and delight in it, not only in the purity of it, but in its beauty as well. I don't think that's something that you learn at school. I think you can get better in mathematics on a school level, but when you're talking about being a mathematician, I think that's definitely a gift of genes or whatever, you know? Whatever your pool is.

The common misconception is that we create films for ourselves. And I really don't do it for myself. I get stopped in the street by people saying, "Do you mind if I say this about your work?" Do I mind? I'm delighted. I do it for you. It's not for me. It's my living, yes, sure.

Bong Joon-ho is enormously sensitive to performance. He knows what he needs to see and that's all he needs to shoot. He is so daring. We don't do that in the west. We shoot everything.

I've never done a [Berthold] Brecht. In the 1960s when the Berliner Ensemble came over [to England] with Helene Weigel [Brecht's second wife], I saw all the Berlin actors. It was an amazing time, very exciting early 1960s.