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.

I'm quite happy to leave it still feeling that way, leave it before it starts feeling like a job. ... I have such fond memories of watching 'Doctor Who' when I was a kid and growing up, that if I've left anybody anywhere with memories as fond, then I feel like I've done my job.

How galling to watch someone who looks like you, who basically is you, do all the shagging you didn't get to do.

It's very hard to be objective about something you're in, especially when you set it up against things that you experienced as a child.

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 think if my eight-year-old self could see me at the Royal Albert Hall winning a prize for playing the Doctor on telly, he would need a stiff shot of Irn-Bru.

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.