Do you think being an only child yourself helps you play these isolated characters?

I have thought about it. I've got a good and very accurate imagination, so I find it easy to put myself in someone else's shoes. Also I'm very, very sensitive to things around me. If I listen to a piece of music and it really strikes me, it will send me these images. I can then use them when it comes to playing a scene. When you begin acting quite young, you're having to make up a lot of experiences you haven't actually had yet. And so you find ways of doing that. Also, a couple of the people I've worked with have said I've got a sort of haunted look about me. Which I think is just to do with my eyes, 'cause they're sort of quite big.

It amazes me how you've been embraced in so many different movie markets around the world, and of course you always look the same. In the books, illustrators in different countries have all had different ideas of how Harry looks, don't they?

It's interesting. Harry Potter's like Jesus in that way. [Pauses] Oh, God! No, okay, no, um.... [Laughs nervously] God, that's a real Beatles moment, isn't it? My point is that Jesus is different in different countries. Like when Christianity was trying to be spread in Africa, all the depictions of Jesus were as a black man. In England, he's a white man, and that's how everyone views him. Of course, he wasn't. He was from the Middle East, he was from Israel, y'know, and would've looked Israeli. And so, it adjusts. The same does happen, I think the world over, for Harry Potter. He does change his appearance from country to country. Obviously he's always going to have the black hair, the scar, the glasses. But each country makes that its own.

I've heard from the Phoenix crew that you really loved hanging out with Gary Oldman, who's back playing Sirius Black, Harry's godfather.

Gary Oldman gave me a great piece of advice once about acting. Which was, ''Don't be afraid to use your own emotions and your own sadnesses.'' Because even if you're using your own thoughts, you've got the glasses on. You've got the scar on. People will see Harry. They'll see Harry being sad, rather than Dan acting Harry being sad. I think that's a very, very good observation.

A lot of people go a bit crazy when they see their favorite actors.

At the premieres it does get a bit mad and scary. I don't think that's cause of me particularly. It's because of Harry Potter. The whole thing is so massive that people lose sight of things slightly, when they're confronted by an actual person who is in one of the films.

What was it like acting onstage with live audiences of strangers, instead of just on a set with cast and crew that know you?

There are a lot of people coming to Equus who are coming to the theatre for the first time, which is great. But some people don't know how to behave. One night a kid sat there in the front row, about 12 years old. Texting, whole way through the play. Put it away and watch! Slightly ironic, considering the play is about alienation.

Do some people come expecting a Potter-ish affair and wind up shocked by the play, which is quite serious and adult?

Some audiences react in inappropriate ways. We've had a couple of very odd laughs. After a certain point, there's nothing funny about the action. And a couple of people have laughed. And I've thought, If you're laughing now, you're not seeing where this is going. Not to tar a whole audience with that brush, but when there are a couple of them laughing, you just think, Really?

But sometimes people laugh out of discomfort.

That is very true. And I'm sure we've had a bit of that in this play! [Laughs] We did have one night where [my costar] Richard Griffiths' agent, Simon — he's just a lovely man — he was sitting next to six or seven born-again Christians, who were there the whole time just absolutely terrified. Just didn't know what to think, which I found very funny.

Have you spoken to Jo Rowling lately?

I went out to dinner with her when she came and saw Equus. She loved it. I knew she was coming, and I did get a little bit nervous, actually. She wants us all to do really, really well for ourselves, in whatever ways we want to, and so I wanted to prove that I was doing well. So I was very nervous when Jo came in. But she loved it. Except, it was the one night that someone at the end threw a stuffed owl at the stage, a little cuddly Harry Potter toy owl at the stage. And I was like, Why, why? Why now? The one night that Jo is here! But there was actually a very sweet message [attached to the owl].