Actor David Thewlis first made a name for himself as Johnny in Mike Leigh’s Naked, and has gone on to make films like Seven Years in Tibet, The Island of Doctor Moreau and Kingdom of Heaven. He and his partner, Anna Friel, have a young daughter and live in LA. Here he talks to View London’s Matthew Turner about Nazi accents, disturbing research and a little film called Harry Potter…

I heard you on the radio recently talking about the research you did with one of the real commandants of a camp. Can you tell us about that?
David Thewlis (DT): Well, not with him personally, obviously. Rudolph Hess, who was one of the commandants of Auschwitz. It was just very useful for me that this document existed – it's an autobiography of his time at Auschwitz. It brought home to me the reality of it and also the detailing of his time with his family: his love of his children and his relationship with his wife, who did not know for two years, the truth of what was going on, even though it was an extermination camp as opposed to just a labour camp. And some very awful and graphic descriptions of what he was perpetrating. So it couldn't have been more of a gift to have and it was very useful.

I like the fact that the accents were all British accents rather than German. I know that you enjoy the opportunity to do a good accent. Were you annoyed at not having to do a Nazi accent?
DT: (Laughs) I wouldn't say I enjoy it! No, I wasn't disappointed. I thought it was good. As the director said last night (at a Q&A), the main reason was not to burden the children with an already very, very difficult job to get those parts right, which they do beautifully. And I don't think it would be the film it is, had they also have had to take on the accents - their performances would have suffered and if their performances suffer, the film suffers and you won't have the same film, so once you've suspended disbelief - because really we should be speaking German, not German accents. So I was very, very happy to do that, because actually I don't enjoy doing accents at all! Well, not many of them.

I'm basing that on the fact that you enjoyed doing the Welsh accent in Basic Instinct 2.
DT: (Laughs) I did enjoy doing that one, yeah. I did that one because there was not much else to do with the part and I thought, well, he's a detective and most of it was 'Where were you on the night of the fifth?' and I thought, well, that sounds nicer if you say it in a Welsh accent. But not much deep research behind that, really.

Being a parent, do you think your response to the material in the film was that much stronger than it might otherwise have been?
DT: Yes, I suppose so. Certainly, in shooting, I mean, the worst thing one can imagine as a parent is losing a child, so that's certainly what I was thinking about, directly, as we were shooting. But I was also having very bad dreams at the time, when I was doing all the research and immersing myself in this period and the ugliness of it, I often dreamed about my daughter being taken away, to the point where I actually stopped doing the research because it was getting a little weird.

What projects have you got coming up next?
DT: The next thing I've got coming out is a film based on a Paulo Coelho novel, called Veronika Decides To Die. Another cheerful one. It's all set in a mental hospital and I'm the psychiatrist. It's directed by Emily Young, who's this great British director – she did Kiss of Life. And then there's this little sort of independent thing called Harry Potter.