I knew it was going to be enormous because of the number of people who bought the books, but, to be honest, I never thought it would be bigger than Bond. Never in a million years.

That's the trouble with anything which essentially has a lot of bits that are physically impossible: You're left, stuck, in the studio. And that's a shame. You're making a movie. You don't want it to stay put, you want it to be a movie - to move.

See, what you're meant to do when you have a mid-life crisis is buy a fast car, aren't you? Well, I've always had fast cars. It's not that. It's the fear that you're past your best. It's the fear that the stuff you've done in the past is your best work.

Believe me, my children have more stamina than a power station.

My kids love it. I thought I was the coolest dad in the world when I got to be in a Bond film, but 'Harry Potter', too? Well, I think I qualify for a medal for exceptional parenting or something, don't you?

I had a very bad time with acid. I did that classic thing of looking in the mirror by mistake and seeing the devil. But I took it several times, because you always think that next time you might have the wonderful time that everyone else is having.

It was quite instant that he wanted Harry's approval. Did you notice that? And the children sort of rescued him this time. It's a great turnabout. That's what happens as your children get older. They do things for you, and it's quite shocking when they do.