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.

Leonardo is the most incredible actor, on the planet, with a couple of people alongside him. Getting to act with him is just [amazing]. I walked away from my audition for that and I couldn't believe that I'd been acting with him. I've worked with amazing people, but my friends freak out that I'm working with him. I freak out in a geeky acting way. They freak out in a starstruck way. He's Leonardo DiCaprio, and his fame is so big. That's a complete tangent about that.

People always say, "You played such a strong character." I remember someone said that to me when I played a role in Shame, and she was a suicidal mess. I said, "She's not strong at all; she's incredibly weak." But "strong" to people means "real." It means you believe that's a person who exists, as opposed to some two-dimensional depiction of women.

When you start playing a character every day for seven weeks, it suddenly starts becoming easier.

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.

My agent in London told me, after Never Let Me Go, because I loved doing that so much, "If you're on a lucky streak and you're doing well, you should only take a part, if you can't bear the idea of anyone else doing it." That's been the case since then, with Drive and Shame and the play (The Seagull), and the stuff that's going on, like Gatsby. I would have been devastated, if I hadn't gotten those jobs.

I don't really think about roles - "dream roles." It's always about who's gonna be the person on the screen or who's gonna be the person on the stage and who's gonna direct it and put it all together.