The truth is, it's very hard looking back... we look at holocaust now with such knowledge and such a sense of the horror of what it was, that it's hard to believe even now that in 1930s and 1940s, before something like this had happened, that it could be impossible to imagine the extent of this horror.

The most important thing is that you have to have the visual effects working for you, instead of you working for the visual effects.

A lot of things change and a lot of things stay the same, they mostly stay the same.

In some ways, many of the skills you have as a producer on independent films also apply to making big tentpole films: You surround yourself with a brilliant director, great script and talented people in every department who are smarter than you.

The films you're making have to be faithful to the material.

Because actually it's really hard to get things made. It takes years. To fight the fights you inevitably have to fight, even when you've produced Harry Potter, you'd better have the commitment and the passion to knock down walls, not take no for an answer.

I look forward to having the time and the opportunity to take on new challenges, but I'm also aware that I've loved every minute of the 'Potter 'experience: to make films for an enthusiastic audience and work with great material.