Harry Potter and the Half-Blood Prince is out this week and you're already filming the last two movies. How does it feel to have the end in sight?
To be honest, I've got a year left of shooting, so I'm not thinking about the end yet. Probably on the last day I'll get emotional, but not for the reasons anyone would expect. Not because I'm leaving behind a character. I will be sad about that, but that'll happen six months after. That's normally when I think: God, I could have one more go at that. Although, to be fair, I'll have had eight goes at Harry Potter by that time. But I'll be sad because I'll miss all my friends that I worked with every day. It'll feel like a tribe splitting up.

You must be starting to think about what you want to do next?
I want to keep acting. I want to test myself. For now I just want to try things and see.

Between Potters, you did the play Equus and a couple of films. Were you looking to do things that were miles away from Harry Potter, to show you could?
Yes, we always knew it was important that I start doing other things to ease people out of the perception of me being one character.

Who do you make those decisions with?
When I say "we" I mean me, my mum and my dad and my agent: we're all very close. My agent Sue [Latimer] is a family friend of 20 years.

Do you worry that people will forever see you as a schoolboy wizard?
A lot of people will be generous and open-minded enough to see me as other people. But I think that to a lot of people I will always be Harry. I'm not going to grow - that's tough luck - but hopefully the change in me physically will help people disassociate me from Potter.

How did you feel when JK Rowling said she was writing the last book?
I think I always knew there were only going to be seven books. Because in the books you get seven terms of Hogwarts. I did have a mild moment of cardiac arrest one day when I picked up my phone and looked at the browser and it said, "Rowling promises eighth Harry Potter book" and I was like "Arghhh! What?!" I saw her the other day and I said, "Jo, you're not going to do any more, are you?" She said, "No, don't worry. No more Potters."'

You've described the new film as being a bit like Trainspotting. You've got to explain that one!
There are a few references, yeah, certainly. There is a moment when Ron takes a love potion and he's suitably loved up. Then Harry at one point takes the potion Felix Felicis, and I was doing a vague attempt at Spud's famous scene in Trainspotting - you know the one where he talks really fast? It's that kind of mentality.

Do you ever step back and wonder how a story set in a boarding school became so popular? Though you're probably not the best person to ask because you're in the middle of it.
Yes - and you're the first person to realise that. I can't tell how far this phenomenon stretches because I can't see the edges. I'm aware of it being a phenomenon, because you can hardly not be when you disembark a plane in Japan and there are 5,000 people waiting for you. That was terrifying. It was completely overwhelming for a 12 or 13 year old. But I do sometimes look back and go: God, how did I do this when I was young? But when you're 11, I suppose you have more energy.

There's a difference between being 11 and having screaming girl fans and then being 17 or 18. How did you deal with it, as an adolescent?
You laugh off a lot of it. You have to dismiss it as being ridiculous. And realise they're not there for you, they're there because you play this character. If I play another role, there won't be 5,000 people to greet me at an airport. It's Harry more than me. And as long as you make that distinction and don't buy into your own hype then it's easier to cope with it.

Did you finish school a while ago?
Yes, almost three years ago. My parents recommended that I stop, funnily enough. We were sitting in a restaurant in Australia and they said to me, "You're going be doing Equus in a month, and you just won't have time to keep going with formal schooling." And so I stopped. I've continued seeing a language teacher twice a week. We just sit and discuss ideas. I imagine it's how Roman children were schooled.

Do you go and see a lot of bands?
Not as much as I want to. It's hard because I'm knackered at the end of the day and I just want to go home. Glass of wine and I go to bed. A friend says this to me regularly: that I'm an old man in a young man's husk. I like that. I am old-fashioned in some ways.

Is that your personality or because you've been doing Potter?
I think it is largely to do with the people I've been around for the last ten years. But even when I was young, people would say I was an old soul. I remember something written about me when I was 12 that said if Daniel Radcliffe wants he could pursue a career as a politician. I'm a real bugger in an argument.

You could do law if the acting dries up.
I could - but I wouldn't have the patience to do the course, that's the thing. I'm easily distracted. And I would also be given to histrionics. I've watched A Few Good Men far too many times to be a lawyer.

You've officially been an adult for two years. Have you got your own place?
Yeah, I have. I'm living in south London at the moment. Southwest. It's lovely. It's a slightly rude awakening, like, "Oh my god! I've got to do so much more for myself." Got to do the washing. But I still live quite close to my parents and take it round there sometimes.

Other child actors have had a difficult time adjusting but I can't see you having a Christian Bale outburst on set.
That shocked me. And I'm not going to judge him because I don't know anything about it. I've always looked up to him a lot, because he was one of those people like Jodie Foster and Elijah Wood that made that transition from childhood actor to adult actor really well. Jodie Foster did it rather brilliantly. And Christina Ricci.

You don't seem primed to go off the rails.
No! I've got good parents, I've got friends, I've had a great childhood, I've had a great time on Harry Potter. It's just been great fun, but people do worry and write cautionary tales to warn me.

Even now?
No, maybe not. But I'm sure some people are still waiting.