Best ever was filming in Barcelona last year, and I had a couple of scenes with De Niro. He's a very shy man. Speaks so quietly that people tend to bend down and adopt the same tone, almost the same voice, whenever they talk to him - watching, you'd think someone's offering to carry out a hit for him when they're just offering him a cup of coffee.

There's not a huge pile of scripts at home. It's what happens to be on the table at that moment with your availability. And then you have no control over when these things come out.

Particularly [Alfred] Hitchcock, who takes his time with everything he says. There's a controlling way in how he speaks because he takes his time to finish all his sentences.

What happens is some of the characters I've played have voices that are so different from my own, that it would be ridiculous if I would dip in and out of that voice in between takes to ask for a coffee, or something. Or to gossip about whatever was going on.

But I think the children of actors share a certain pragmatic approach. One is denied some of that 'running away with the circus' element of being an actor.

There is this miraculous thing I heard Hugh Grant talking about - the thing about screen acting is that you can read people's thoughts. You are trying to register something inside and usually the eyes in cinema are where you will register that.

When I told people I was going to be doing the movie and the voice of Dobby, they were kind of awestruck, the people who knew about Harry Potter. I felt rather guilty that I didn't really understand the scale of the job I was about to take on. Now, I am well aware of what I'm doing, and actually, it feels a very serious acting responsibility.