I'd like to do a play, but I can't find the right thing. I don't want it to be a starring role. I just want to play a really interesting character.

I've never been obsessed with celebrity or star-struck or anything. I met Penelope Cruz when we were in Toronto, who I think is a goddess and an unbelievable actress, and she introduced herself. As she walked away from the table I had to take a deep breath, which was strange because I've never had that with anyone.

I've always played characters that were younger than myself.

I was quite straight-laced. I was quite academic until I was about 14 and then I went to boarding school where I had the opportunity to continue to be very academic, but got less interested in it and became more involved in acting. And then when I was applying for universities I used a couple of places on my UCAS form to apply for drama school without telling anyone... but didn't get into drama school. But that was the most rebellious thing I did.

On film sets I can see everyone, and I really still find that so difficult.

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 never get recognised here in London, which I like. Once a year, someone comes up to me and asks if I am 'so-and-so's niece' because they think they recognise me from somewhere. I like that.