Pottering about

'IT'S like a little city," says David Heyman, sitting in the heart of the magical place where he's spent most of his last six working years. We're at Leavesden Film Studios in Watford, 20 miles outside London, in the former Rolls Royce factory that's become home to the Harry Potter movies taken from JK Rowling's bestselling books.

The news that Harry Potter Land is being built in Universal Studios in Florida seems unnecessary as the campus where the films are shot has everything the most avid Potter fan could want, Hogwarts and all.

Millions will be spent on the US theme park, due to be open in 2009, but it won't be the real thing. No visitor will be able to say they've sat in Dumbledore's real chair as I did while visiting the set of the fifth film, Harry Potter And The Order Of The Phoenix, last summer.

The makers of the Potter franchise have made Leavesden their home, leaving sets standing between films. "It's been a real gift this place, because we can keep the sets up. Some have improved with time. In the Great Hall, the gargoyles that hold the flames have got blacker and grimier and dirtier with each film. It's an organic thing, it makes it more lived in."

We've watched, too, as the young cast get older and more lived in. The three leads - Daniel Radcliffe, Emma Watson and Rupert Grint - have grown up on screen. The fresh-faced youngsters have developed into teenagers, with Harry getting his first screen kiss in the fifth Potter film, released in mid-July.

Radcliffe is even contemplating life after Harry. "It'll be strange, won't it?," he says. "Very liberating in a way, but I love being here and have learnt an enormous amount. Knowing there're seven books, that's a definite goal to hit."

Unlike other child actors, Radcliffe hasn't succumbed to pressures of early fame and fortune, despite his pay cheques making him one of the richest young men in the country. He's kept a level head, although he's not beyond having fun. "I love playing games with people," he says.

"There was one day where JK Rowling came on set and I had half an hour talking to her, then I went back and made out to the extras that she'd told me the ending."

Radcliffe fields questions like a pro, more efficiently and intelligently than many who've been doing it a lot longer. Some young actors might get embarrassed or shirty when asked, by a girl from a teen magazine, if tongues were used in his first screen kiss.

"No," he says. "It was a lot more clinical. It's like being in any scene really. If anything, it was disappointing about how unsexy it was."

Since we spoke, he's carried out his plan to strip off and appear totally nude on stage in the play Equus. All very surprising for someone who admits he's only just becoming more confident with girls. "I was never shy but not particularly self-assured, and found it very hard to keep eye contact. But I'm getting better," he says.

His co-stars have reason to celebrate too. Emma had heard that morning she'd bagged eight As in her exams and talks of wanting to go to university. For the moment, she's signed up for the final two Potter films.

The balloons and neatly-packaged parcels on the table in the canteen at lunchtime are a clue to Grint's reason to celebrate. It was his 18th birthday. He's already left school and, like Radcliffe, is eager to do other work, having already starred with Julie Walters (his Weasley mother in Potter) in the film, Driving Lessons.

Still the laidback lad I remember from the first Potter film junket, he owns up to a problem with giggling on set, worried that laughing will ruin the take.

All three have learnt much over the five films, especially having different directors on the last three. Goblet Of Fire director Mike Newell was "not afraid to be rude or swear if you got it wrong", says Grint. David Yates, who's helming Order Of The Phoenix following TV success with Sex Traffic and State Of Play, is "really good at telling what you want to do", he adds.

The scene he's directing today is set at Grimmauld Place, where Harry meets Siris (Gary Oldman), the Weasleys and the rest of the Order of the Phoenix. It's a small kitchen setting, tiny and enclosed compared to the Great Hall at Hogwarts. The detail is amazing, although it doesn't have a ceiling, which is added digitally at a later stage.

Heyman believes that new directors are one of the things helping to make each one fresh. "One thing that's very important is the producer has to be guardian of Jo's vision but give the director freedom to make the film he wants. You have to allow them to bring their own vision to it," he says.

In the Order of The Phoenix, 15-year-old Harry goes from apprentice wizard to a leader of men, assembling an army to fight the dark forces. "There's an edge, and we'll continue to get edgier. You're dealing with a kid who is 15 and all the turmoil that brings. Dan has got better and better with each film. His experience away from Potter informs his work," says Heyman.

A lot of people have come to the books from the films, and vice versa. Each is helping the other, he says. "Jo, in her mind, keeps them very separate. I call her up to make sure we don't do anything to mess with her fiction. There was something we were going to cut and she said 'I'm not sure you should do that'. She gave me a hint it might be relevant later on."

In another part of the studio, Bafta-winning set designer Stuart Craig is overseeing the construction of the Ministry of Magic. The tiled exterior looks magnificent, although he reveals it's only MDF with a good lacquer finish.

"Even though it's a magical place, you try and give some kind of authenticity and credibility to it, so we went looking at some of the more interesting parts of London Underground. One thing a lot of them have are fantastic ceramic tiles. So I thought 'we'll nick that and run with that'."

Inspiration comes from the most unlikely sources, such as a Burger King in London's Tottenham Court Road. Craig has borrowed designs from this Victorian building for the ministry offices.

He created the world of Hogwarts for the first film. "We looked at the oldest buildings and they are, of course, in Europe, the great cathedrals and the Oxford and Cambridge colleges. We used them as locations and also stole from them," he says.

Heyman made Rowling a promise on the first Potter film to respect the spirit and intention of the books. There was always one expert to ask if they got stuck creating the world of Hogwarts - the author herself. Craig recalls a meeting before the first film. "I was asking questions of geography, 'where is this is relation to that?' and she literally drew a map of Hogwarts," he recalls.

"A map of the world showing the lake, the castle, Hogsmead village, Hagrid's hut and the railway station. All of that is very specific and so that was spelled out. I have a print of that map upstairs and we still refer to it."

Harry Potter And The Goblet Of Fire opens in cinemas on July 13.

The final book, Harry Potter And The Deathly Hallows, is published on July 21.