Is there life after Harry?

It's a bit like watching someone's children growing up. Another Harry Potter movie, another chance to see how the three young stars are coping with starring in the successful screen franchise.

Daniel Radcliffe, Emma Watson and Rupert Grint were unknowns when they faced the international Press at the launch of Harry Potter And The Philosopher's Stone back in November 2001. They'd been chosen to play the trainee wizards whose adventures feature in JK Rowling's phenomenally-successful series of novels that are eagerly read by children and adults alike.

One year later, a little older and a lot wiser, the trio were back in front of the media to talk about the second film, Harry Potter And The Chamber Of Secrets. "What a difference a year makes," I wrote, noting how much the children had grown up and become more confident.

Now here we are again, in the majestic hall of the Banqueting House in London's Whitehall to talk about the third and darkest film, Harry Potter And The Prisoner of Azkaban. Once again, you can't help but notice how the three of them have matured into teenagers, both in looks and attitude.

A few things haven't changed. Red-haired Rupert, 16 in August, is still laid back and says "wicked" a lot. Daniel, looking naked minus Harry's trademark glasses, remains the more serious one as his 15th birthday approaches. Emma, the baby of the bunch at 14, is growing up into a very attractive young lady.

If success has gone to their heads, they don't show it. All three talk about how much fun they have making the films and how much they enjoy the whole process. They even attempt to answer such philosophical questions as "What does growing up mean to you?" posed by a member of the foreign Press.

Daniel deals with it rather smartly. "I won't know until I become an adult," he says. Rupert, who plays Harry's friend Ron Weasley, notes that his voice has got deeper and "I'm a bit taller". Emma, the screen Hermione, turns the question into one she can answer. "Do I long to be an adult? No, I'm having a pretty good time at the moment. Being a teenager is an interesting age, a time of discovery, making mistakes and learning from them. I intend to enjoy it."

There are older, more famous actors - including Gary Oldman and Michael Gambon - as well as producers and director Alfonso Cuaron on the platform with them, but the youngsters attract most of the questions.

Chris Columbus directed the first two movies, with Cuaron taking over for the third.

He asked the young stars to write him an essay about their character before filming began. Daniel can't remember what he wrote, although he does recall filling a page of A4 while Emma wrote "about 20".

She ticks him off: "It gets more every time you tell it. Ten, 12, 15, now 20. I have big handwriting and use a lot of space," she pleads.

As for Rupert. "I forgot to do it," he confesses.

Working for a new director didn't faze them. Cuaron was probably more nervous than they were. After all, he was the newcomer.

"Everything we learnt with Chris, we now had a chance to bring it back for another director," says Daniel. "That was a challenge in itself, and helped us to evolve a lot."

Rupert found it "a bit weird" at first because they'd got really close to Chris. But he adds that "Alfonso is wicked", which is a big compliment by his standards.

They've become used to being in the public eye but the American premiere earlier this week showed that Daniel has moved up a notch and become a teen heart-throb. Dozens of girls in the crowd outside the cinema screamed, shouted and held up banners proclaiming their love for him.

This must be overwhelming for him, as he even took time to get used to watching himself on the big screen. "I saw the film with some of my friends and was sitting in the front row. The last frame is my face and it looked as if I was going to eat the front row of the audience," he says. "It's kind of scary and surreal."

One frightening aspect of filming the third Harry Potter was acting alongside Gary Oldman, who plays the sinister Sirius Black. Daniel is a huge fan of the actor. Shooting a scene with Oldman, David Thewlis, Alan Rickman and Timothy Spall was particularly intimidating "because they're such fantastic actors".

All three maintain that being stars isn't what matters. The money's not important either, mainly because it's in the bank and they can't get at it until they're older.

"I'm 14, I don't have any major use for it," says Daniel. "I buy a lot of CDs. Being a movie star doesn't matter to me - I like the work."

Emma adds: "I don't feel like a movie star except maybe two or three days a year."

Rupert says it's weird (as opposed to wicked) and that money is nice to have. He's bought himself a quad bike which is cool (as opposed to wicked).

They don't feel they're any different to others their age. "We're maturing the same way as any teenager in the world. Other than being on a film set, it's not much different. I don't think we've lost anything or it will hurt me in the long run," says Daniel, whose pre-Harry roles included the young David Copperfield in a BBC-TV production and appearing with Pierce Brosnan in the film, The Tailor Of Panama.

"I've known Dan and Rupert from the start and they're the same people they were when we started, and I hope I am too," adds Emma.

Shooting on the fourth in the series, Harry Potter And The Goblet Of Fire, started two weeks ago. All three hope to continue in their roles as long as possible.

Producer David Heyman says he's been misquoted as saying they'd get too old for the parts. "I said there may come a point where we're either unable to keep up with the ageing of Dan and Emma, or they may decide to move on. It's a possibility," he explains.

Daniel adopts a "whatever happens, happens" attitude, believing it's too early to talk about the film of the fifth book. "I love doing the films and am interested in going on to other things at some point," he says.

"I'm not saying it would be easy to see someone else take the part after playing it for four films, but if it happens it's something I'd have to get used to."

He then proceeds to kill off his character by suggesting that Harry might die at the end of the series in the seventh book because of the young wizard's connections with his arch-enemy, the evil Voldemort.

"Harry and Voldemort have the same core in them, which you see in the fourth book. The only way that Voldemort could die is if Harry dies as well."

As for life after Harry Potter, all three want to continue performing. "I love acting, singing, dancing. Hopefully, I will end up in some area in film or maybe the stage," says Emma.

Rupert would like to carry on doing films, even if it means foregoing his childhood ambition - to be an ice cream man.

Daniel loves acting but there are "loads of other things I am interested in. It's something I would love to go on and do, but you have to see what happens".

* Harry Potter And The Prisoner Of Azkaban (PG) opens in cinemas on Bank Holiday Monday.