The thinnest I've ever been was after I had my appendix out, during the London run of The Seagull. I went down to 112 pounds and realized my brain doesn't work when I'm that thin, so I can't do my job. That's why, when I came out here, I never had that whole Hollywood pressure thing. I never said I wanted to be a lead actress; I never said I wanted to be a film actress. This need to trump everyone bewilders me. I'm only 25. I'm not better than anyone. I just want to watch other people and learn to be good.

It's actually easier to play a leading role than it is to play a supporting role.

I was trying to find ways of not being pigeon-holed like that. I didn't want to be tied down by my accent. I wanted to play Americans. I don't want to ever be doing the same thing twice, and I just didn't want to repeat myself.

Posing on the red carpet feels like you're selling something that has nothing to do with you. If you do it with someone else, it's like we're saying, 'Oh! We come as a pair! Would you like to buy both of us? We're available for weddings and Bar Mitzvahs!'

I remember in 'Pride and Prejudice' I had to do a scene where I broke down. And before we filmed I spent like three hours imagining my mum's funeral. Actually, she's very much alive, happy and healthy. It was really horrible.

I've always been quite careful about what I wanted to do. I've just never wanted to revisit old ground or do something that's easy. I want to do something that I would look at and go, "I don't know what to do!" The most exciting thing is when you're a bit scared, so I'm looking to find something that's really terrifying.

I wanted to be in a Baz Luhrmann film. It's just extraordinary. He's so amazing at what he does. He makes the most incredible films.