Philosopher's Stone video game revisited

The great thing is because there isn't actually a [HP] film [this year], we've got those extra few weeks to just polish the game. If you played last year's Chamber of Secrets on next-gen, this might feel superficially similar, but it's like Zelda on GameCube and N64 - this is a completely new game. And that's what we want to do, create a big franchise [like Zelda].

There's some stealth sections, some flying modes, but probably 80 percent of the time there's this sort of arcade adventure, it's almost Zelda-esque. We're not afraid to admit our influences - it seems a lot of people try to reinvent the wheel every time they come to game development, but there are games out there that we really like, that we think are done really well.

During the day you'll attend lessons, during the night you'll be sneaking around, trying to uncover more of the plot. The game itself is relatively linear in that it follows the story of the book, but what we have are sub-quests that you can go on, there's a notice board with students who have lost things that you can track down for them.

But you start off by arriving at Hogwarts at night, and there's basically a task that needs to be done for each day and each night.

We've worked closely with JK Rowling. She's not a gamesplayer, she doesn't know much about games, but what she does bring, obviously, is an encyclopaedic knowledge of Harry's world. She has approval rights over everything, so if she doesn't like something she just says change it.

But she's great because she's obviously planned out the characters and the happenings, even things that aren't mentioned in the book; for instance there's these creatures, the Gytrash, that don't actually appear in any of the books so far but she's given them to us, exclusively for the game; it's great to have stuff like that.

We give her requests for things like more creatures or more spells, things like that, and she's given stuff to us that, we don't know, maybe she's going to use in her later book, or she might just be giving to us for this game, but it all comes from her.