Following LEGO Harry Potter Years 1-4, what sort of things did you want to improve or expand upon?
"The first game was a different direction for LEGO, because we wanted to create that experience of going to school, being a wizard at Hogwarts and it was very light-hearted and jovial, like the first films are really.
"So for Years 5-7, the big change is that dark times are coming, now it's not about learning magic and having fun with it - although it is - [but] it's about learning new magic that you're going to be able to take and fight the forces of Voldemort with.
How is the tone of these later films worked into the game?
"A lot of it is the mood and atmosphere that you create. First and foremost, the LEGO games are always about fun, and fun interactions and humour and making people laugh. But at the same time, there is that darker nature of everything, which actually means it's easier to create fun from [it].
"You've got that massive disparity in emotion, from fear and trepidation or that element of danger, so being able to flip that on its head and create a laugh, it's actually a lot easier to do. Especially with some of the moments we're re-enacting, whether it's [the] deaths, or Harry coming under attack from Voldemort, it actually makes it easier to parody really. So it's actually been quite fun and exciting."
"What we've done for this game is make it bigger. In the first game, you were in the walls of Hogwarts, and you could explore Hogwarts, go off the beaten track, you could go to your lessons and your story events, or you could go have a bit of fun.
"We kept that, because that was such a massive positive. And instead of just keeping it, we've expanded it. You can actually walk outside of Hogwarts, you can walk to Hogsmeade Station, you can get the Hogwarts Express, go to King's Cross, explore King's Cross, go out into London, wander around London.
"We've actually linked it all up, so now it's not just Hogwarts, the whole Harry Potter universe is there to wander round and explore. There's Hogsmeade and Hogshead, and you've got the whole forest hub area, because obviously Deathly Hallows Part One in its entirety is set outside Hogwarts, so we had to make sure we captured that.
"Now it's created an even bigger hub world, which still is ram-packed with interactions and fun and fiction points that hardcore fans are going to pick up on. It was really key for us that we took that and advanced it and took it forward."
"Well, it's a similar sort of thing. Again, because we can't assume that people have played the first game, the first part of year five we lock down Hogwarts so it gradually unfolds and opens up. But pretty soon into year five you've got access to pretty much everywhere within Hogwarts.
"But we keep enough back so that throughout the course of six and seven, we're always offering something new to the player, there's always another area getting unlocked or opened up, or another area to explore. We've given more freedom, but at the same time, just for the early stages, we direct the action because it could be that someone has never played any of our games before, let alone Harry Potter. We still need to make sure we don't lose the instant pick-up-and-playability of the LEGO games."
Most of book seven is set outside of Hogwarts. Does that mean that it's quite linear as the characters are on the run?
"But if you go into the tent via the Marauder's Map, you actually go back to Hogwarts, but when you link into Hogwarts you're playing as Seamus, Neville and Ginny. So you can still get to Hogwarts and explore. It's not linear, because you can still go and explore everywhere, but it's just obviously you go around Hogwarts as anyone but Harry, Ron and Hermione."
Does that mean if you can return to Hogwarts early, there are new objectives there?
"Oh absolutely. There's always new stuff to do in Hogwarts, and because there are always new characters to unlock in free play, right up until the end of the game, there's always new stuff to access and explore and entertain people. Areas are never devoid of interactivity, there's always something more to do."
"Yeah, basically within Deathly Hallows there's the Peverell brothers sequence in Part One - which has a really gorgeous art style, that animation - we wanted to try to do something that was also different.
"So as an experiment, we wanted to do this Limbo style level, and it was always going to be penned as a bonus level, a giveaway at the end of the game. We had this pop-up art style, this unique 2D platforming. But as it came together, we thought this is really good. So rather leave it as a bonus, we actually ended up sticking it into the main level.
"So part way through that level, where you expect to see a cutscene explaining the Peverell story, you actually get dropped into this 2D level. And because it's so unexpected, it's just like 'Wow, what's this?'
"And the cool thing is that actually that's the downloadable Xbox Live and PSN demo, so when that goes live about a week before launch, people will be able to play that and see it, and we think it's a massive success because we think it's so different. A lot of work went into that just to try to do justice, really, because in the film it's so nice, and we wanted to mimic that."
"Yeah - because the handheld versions are handled by our satellite studio TT Fusion, they specialise in that. What they've done is taken our level and level designs and mechanics and stuff, and adapted them to work on handhelds.
"The 3DS actually, because I got to play it the other day, the finished version, looks really really good. I was surprised by the visual quality on the 3DS, and the levels feel very similar. It's very, very close to the console version, and I think it will surprise a lot of people because they won't be expecting quite as close as it actually is. It's actually very, very good."
Finally, why do you think the LEGO games are such a success?
"Well, I think the success of the LEGO games is down to what we actually aspire to and achieve. They're games that people can play together. There are very few games that you can play co-operatively with a child and our games allow parents to interact with kids, gamers with non-gamers, co-operatively with very little pressure. There's no reliance on anyone being a great gamer.
"They also know there's a lot of fun in there. We never do anything that's offensive or could be deemed too severe for kids. We hit the target audience we get, but we because we do what we do, a lot of older gamers enjoy our game as well.
"It's almost like a Pixar film in a way; it looks cutesy and kids love it, but there's also hidden layers in there that appeal to other people, and if someone is a fan of the IP, whether it's Batman or Harry Potter, they'll love playing the game even if isn't something they'll necessarily think of when they're playing games.
"The number of people that we have contact us saying 'We played this and it was great, thanks, because I got to play a game with my girlfriend', or 'I ended up playing with my nan', or whatever it might be... I think it's just the wide range in appeal, and long may it continue."
LEGO Harry Potter: Years 5-7 will be available on Xbox 360, PlayStation 3, Wii, PSP, DS and Nintendo 3DS from November 15 in North America and November 18 in Europe.
> Read Digital Spy's review of LEGO Harry Potter: Years 1-4
Watch the first trailer for LEGO Harry Potter: Years 5-7 below: