And of course I've got kids of my own now, and they love me being in the Harry Potter films. I'm now part of a phenomenon. You become incredibly cool to your kids, and you get a young fan base. So you became the cool dad at school. You're suddenly hip.

At 23 it was all about acting. Today it's getting my kids to school, making sure that they've done their homework. I'm in my fifties, and I'm turning into a square.

How many movies do you see when you can say this director really knew what film he wanted to make? I can count them on the fingers of one hand.

Well, I needed the work - that's the honest answer. I haven't worked for a while, a couple of years. So I thought it would be nice to get back to work and earn some money.

How do you remember all those lines? By forgetting everything else.

Each role you play, they set a bar of challenges that you meet. And in the past, I've played characters that emotionally expressed themselves a bit more in a physical way. It was a joy, actually.

I'm still a member of the Empire! Although I sometimes feel like an American with a British accent - you get contaminated after so long.