Q Do you work with [author] J. K. Rowling when you're hammering out a script, or do you have total freedom to adapt as you please?
A I'm a little too free. Jo's become a really good friend - one of my best friends - and I wish I had more of her. When I first got to know Jo, she wasn't married, and now she is married and has kids, so she's gotten a much bigger life.
Now, we mostly correspond through email, and she's very responsive and very helpful. But from the beginning she has always said to me, "I know the movies will be very different. I know they can't be the books, and I don't want them to be the books. The only thing that matters to me is that you stay true to the characters."
So that's always been the one thing I feel very much in charge of, protecting the characters, and it's the thing that upsets me the most when I feel the characters are being violated. That's when I push back hard.
Q Has that happened in any of the films?
A There's one moment in The Chamber of Secrets that I don't like, where Hagrid enters Hogwarts at the end of the movie and the whole group of assembled students applaud him. That would not happen.And it really upset me. I felt it was a real violation of character.
And that was odd because [director] Christopher Columbus is a Potter fiend. He carried the book around with him. You could never catch Chris on anything. But I think Chris felt that he wanted the release of that moment. It was a mild disagreement.
Q What kind of things do you run past Rowling?
A A range of things, even something really simple. I once asked about the 12 uses of dragon's blood, which is referenced in the books. There are writers who would write "12 uses of dragon's blood" and not have a clue what they are; it just sounds cool. But I emailed her to ask (and this was 10 years ago), and 25 seconds later I get an email back with a list.
Q Do tell. She's only mentioned "oven cleaner" in interviews.
A One is an oven cleaner, yes. Another is a spot remover. ... It was really amazing. Really, the books are only the thinnest surface of what she knows about the series.
Where Jo is helpful in a more serious way for me is when I want to know more about motivation or background, when Harry realised certain things, when characters understood things.
There was one case where I was violating a plot thing - it had something to do with Dobby, I think - and she said "No, you don't want to do that", as she knew what was to come.
She's a great resource for problem-solving . . . she can help with complicated things. Though her plots are so fiendish that they're really difficult for cinema.
Q What, if anything, can you say about the climactic moment between Snape and Dumbledore? In the book, it's a short but intense scene.
A It is informed by everything [Potter readers] have come to know is true. So if you watch the film carefully, there are performance moments that are quite extraordinary, Alan Rickman (who plays Snape) especially.
There is something we added that you can look forward to, a short scene between Harry and Snape prior to the big event. It'll be interesting to see how it plays to the audience. It should be a haunting moment for Harry.
While I was writing, I just had a notion about a moment between him and Snape, something Harry could look back on and question as to why he didn't act differently.
Q I've also read that most of Dumbledore's memories of young Voldemort, then Tom Riddle, have been cut from the film. (Not to mention Dumbledore's funeral!)
A In my original draft, I had every single memory but one, I believe. I even dramatised a couple of things that weren't in the book in terms of Voldemort, like the death of Tom's parents, things like that. I'm a Harry Potter fan, so my first drafts tend to reflect that, in that they tend to be long and all-inclusive.
When [director] David Yates came in, he had a very specific point of view, which was that he wanted to showcase Voldemort's rise without getting overly involved with his past as Riddle. He didn't think that most of the memories would be as compelling on-screen as they are on the page.
He liked them in the script, but he really felt that in the movie experience Voldemort's story was more important than young Riddle's. We went back and forth on that for quite a bit. But he was very convincing, and I think it wound up working out well.
Q Are there any other changes or additions that you can talk about?
A I know one thing David is very proud of is getting Quidditch right. I do think it's the first time that it feels like a sport. And it's comic, which is fun. Rupert Grint [who plays Ron] is great. We also do a lot with the kids coming of age, navigating sexual politics and all that.
It's pretty interesting to see these characters doing that because the movies have always been a bit chaste, and they continue to be on some level, but there's more happening in this one. You realise how complicated it is between boys and girls. It's a lot of fun seeing Ron navigate his first girlfriend.
Q How does the coming together of Ginny and Harry play out when we've all fallen for Cho Chang in the previous films?
A It's interesting in the way it's played out. I'm very happy with the moment they consummate their feelings. It was a nice scene and David did it really well. It's sweet.
For any longtime Potter fan, it's now that you begin to see people coming together, but in doing so, it strains the old relationships and the relationships that are the truest and the most trusted. That's potentially dangerous, but it's also a part of growing up. You have to strain those relationships to realise how important they are.
Q How satisfied are you with the finished film?
A I haven't seen the final version. It was not fully scored when I saw it. But I liked what I saw a lot. It's quite powerful, and genuinely moving at times. Even at times people might not expect. There are some intense emotional moments. It feels more mature.
I'm very excited about the next two movies because they're even more mature and the kids are older. Half-Blood Prince is quite a leap from Order of the Phoenix. It's quite different. It's not an action movie in the same way. But the last two films will be hugely different from all that have preceded them.