Were you given a set of guidelines that you had to cohere to some extent with the three previous films?

I think that the studio and producers were very liberal about that. I didn’t feel that at all. Once in a while there was, “Oh no, you don’t have a wand like that.” Depending on whether I was feeling bloody-minded or not I would accede to that or kind of growl at it, “Why can’t you have a wand like that, who says?” But it was only ever the details.

There was no kind of orthodoxy – except of course you were there to put a famous novel on the screen, therefore you can’t change it that much.

There were a couple of times, where, particularly in the structuring of the Voldemort’s story, we were having real difficulty fitting in precisely the line that Jo had written. She said, “Fine, change it.” I think she knew we wouldn’t have changed it out of all recognition. She knew we would be careful and respectful. It was sort of relaxed actually.