How did you first come across Joe Penhall's original play for "Some Voices"?

I never saw the play, which I'm glad about. My agent had heard the script was around, and he showed it to me. I put my hands around FilmFour's neck, and said "I'm not letting go until we start filming".

What did you discover about schizophrenia while making the movie?

People like to think of it as two minds, a split personality. The thing I understand about schizophrenia, is that when your "attacks" come, you have problems getting reality into order. The distorted reality is very scary, I think. You do get people who go round and slash others with a kitchen knife - but they're the ones who get reported, I guess. Sometimes it's actually quite fun, because it's like taking really good LSD. But basically, you're locked in a dream you don't have control of. We all go a bit loopy sometimes, but for him, he's just showing an extreme version of what we all feel.

The film is set in Shepherd's Bush - any reason?

I live in Shepherd's Bush. The play was set in West London anyway. But almost for me, I wanted to know where it was set. I wanted it to be an antidote to "Notting Hill". It's actually the very next district to Notting Hill. I don't think you'd bump into Julia Roberts in Shepherd's Bush. [But] you never know.

Check out the Edinburgh International Film Festival website and the BBC's Edinburgh Festival coverage.