It gave us nine months to get the effects just right.
Quidditch is much more dynamic and the characters are much more integrated into the background.
The characters of Dobby and the Basalisk and the spider feel like they are a seamless part of the world and that was important.
Did you worry that this film might be too scary for young kids? The basalisk scene was intense and the spider scene was - wow!
Once we'd completed the film we showed it to 250 school children and their parents.
The kids ranged from seven to 13 and we asked them afterwards if it was too scary.
Not one kid raised their hand.
We asked the parents and not one raised their hand.
We asked if it was exciting and they all raised their hands and said 'Yes it was exciting - we loved it! Was it scary? No, it was the good kind of scary - we loved it.'
Kids love to be scared but they don't like to be disturbed. There's a fine line but I think we've solved it in this one.
I know my five-year-old daughter loves the film so I feel pretty comfortable that it's OK for kids.
Tell me some of the difficult cuts you had to make in this film to get the running time?
We actually made the cuts from the screen play rather than the film which hurt us internally but it didn't hurt the film.
We had to cut the deathday party which was Nearly Headless Nick's 500th anniversary of his deathday which was essentially a party of ghosts.