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.

You always get told how important the premiere and doing the press is, but I have suspicions.

If you ever have the good fortune to meet Tippi Hedren, she's an amazing woman. You can't quite believe she is the age she is.

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.

Hitchcock is a big ask. I am playing someone significantly older than me and someone significantly bigger than me. The stuff I find very interesting is why certain physical things have come about. How can he be light on his feet when he is so big? How can his weight vary so much? Where does this rather beautiful voice come from?

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.

You can't deny reality just because you can't explain it.