When you're playing a real person there's a balance between playing the person in the script and playing the person as he was in life. You have to be respectful and true to who that person was, but at the same time tell the story in the film.

If you speak in a different accent, you begin to move in a slightly different way. You think in a slightly different way. It's part of trying to find what makes a character.

There's a morality... I think there's a moral compass but whether that comes from religion or just from being a good person, and where one starts and the other begins... I'm a good person, I hope. But I'm never as good as I want to be, never as nice as I want to be, never as generous as I want to be.

I remember a conversation with my parents about who the people on the TV were, and learning they were actors and they acted out this story and just thinking that was the most fantastic notion, and that's what I want to do.

It has to be said that the bad guys are often more interesting than the good guys because you get to indulge part of your nature that hopefully gets subsumed most of the time. But I just like playing interesting characters, and variety's the spice of that, as it is with life, I suppose.

Getting the call to be in The Goblet of Fire was like being welcomed into the most exclusive upper circle of some elite actors' club. You sit on set with the cream of the National Theatre and the RSC, all clutching wands or wearing witches' hats.

And the very fact of how you speak somehow influences who you are. The way you move, the way you think, it seeps into your being, and it's quite hard to really break that down entirely.