"In the second film, there was a shot where I had to hitch my trouser legs up to show I'm not wearing socks, and at 12 my legs were way too hairy, and they said, 'Nobody's going to believe any 12-year-old would have that much hair', so they had to shave two inches up from my ankle."

Of the three leads – himself, Emma Watson and Rupert Grint – who does he think was the best actor? "I think we were all good at different things. Rupert was the most outgoing of the three of us; he had this confidence when it came to comedy, and he still does. My tendency is to underplay stuff and sometimes I look at the films and I know I thought I was being subtle at the time, but actually I'm just doing bugger all. That's a learning curve. You can't dwell on the things you're not happy with, though; you've got to move forward and get better."

"I can't put it down to anything more than that I've got weird taste. There have been plenty of weird roles so far, and more to come, I hope. I pick films based on scripts and directors and parts. I think I've got good taste, but it's slightly left of centre. I'm not interested in making films I've seen before. There's nothing more exciting to me when I read a script than originality. That's all it's governed by; there's no master plan to distance myself from Potter with every role."

"I know that Potter is going to be with me for the rest of my life, so to try to set a goal where nobody talks about that any more is stupid. It would be like… Paul McCartney might have gone on to do a lot of other things, but people are always going to want to talk about the Beatles. It's just a fact of your life, so you can't get annoyed by it or resent it. You have to embrace the fact that you were involved in this incredibly cool thing that did wonders for the British film industry and though you might not always be happy with the work you did on it, the opportunity it has given you to forge a career for yourself is amazing."

"Yes, I think I am quite hyper. I think if I'd been born a few years later, I might have been diagnosed with ADHD, but I missed the boat for all those diagnoses." If you shut your eyes, you could be listening to a sweet old man looking back on a distant past. "I always feel sorry for people when they say school's the best days of your life. It really isn't. If it was, you must have a terrible life." He coughs like a consumptive. "I never understand that. That was one of the things I loved about Potter initially, it got me out of school."

"No, I knew I was signing on for the first two, that four books had come out. Warner genuinely didn't know at that stage if they were going to make more than one film. If it flopped, then they certainly weren't going to put up all that money again." Did he ever consider exercising his opt-out clause? "By the third film, I thought, if there's a time to get out, it's now; there's still enough time for another actor to come in and establish himself. For a while, I thought, if I do all of them, will I be able to move on to other stuff or should I start doing other stuff now? But in the end I decided I was having way too much fun. And actually there aren't many great parts out there for teenage boys, certainly not as good as Harry Potter."