The Harry Potter stars may not be heading for lives of fame, wealth and happiness, as former child actors tell Leo Benedictus

'We were all at home doing our Saturday-morning chores when one of Jake's little friends from down the street came by and wanted to know if he could come outside. I told her: 'No, you know it's Saturday. Jake has to do his chores first.' But she looked at me real funny, so I asked: 'What's going on?' Then I stepped outside and saw our yard was full of people.

"It was a terrifying moment," says Lisa Riley, mother of Jake Lloyd, the child star of Star Wars: Episode I - The Phantom Menace. "There were teenagers and adults out there, everybody. We're talking about 50 people, which is a lot of strangers to have in your front yard when you're wearing sweatpants and rubber gloves. Jake was inside, trying to vacuum. We moved within a week."

Riley can now laugh about the morning in October 1998 when her son had his first taste of fame. But then the family has had plenty of time to get used to it all: for the past two years they have even been able to go out in public again. When Jake got the part of Anakin Skywalker everyone knew he'd have some attention to deal with, but nobody expected such a reaction when the first teaser poster appeared, a full seven months before the film's release.

Daniel Radcliffe, the 14-year-old who plays Harry Potter, has been growing up with fame for the past four years, but this week even he pronounced himself astonished at the deafening reception he received at the new film's première in New York. "It's really, really, really scary, but it's brilliant," was how he put it.

If the experience of other child stars is anything to go by, he and his co-stars are in for more scary moments. "We had strange letters," says Riley. "We had people following us around. We had all of that. There are a lot of paedophiles out there, you know. They got in touch. Crazy people, too. And then there were the religious fanatics, who thought Jake marked the second coming. I was like, no, trust me. He's not."

The Potter children can expect things to calm down as they get older, of course. But that transition can be a difficult one: today's fame will never disappear, but its sparkle may curdle in to a taint. It is an experience Adrian Hall - who, aged eight, played Jeremy Potts in the film of Chitty Chitty Bang Bang - is all too familiar with.

"There was a long period from the beginning of my teens through to 21 or 22 when it was better not to mention it, because I was trying to establish a career as a serious actor. And the minute they see that on the CV you get categorised as a child star, and that's all. In the end your own negativity takes over, so you mention it in such a way that they already see it as a negative thing." Afterwards, Hall continued to act, mostly on the stage. He managed it with some success before moving in to teaching 15 years ago.

"It's never going to go away," Hall says cheerfully. "It'll be on my gravestone, but there comes a point when you have to accept that. If you don't, then you drive yourself insane and hang yourself in a motel room."

If the Harry Potter films retain their popularity as Chitty Chitty Bang Bang has, Radcliffe and the others will also have to get used to a constant demand for public appearances and reunions. To Debbie Turner and the rest of the Sound Of Music children this has never been a problem. "Whenever I get the chance to do something Sound Of Music-related that's always fun," she says, clearly still enthusiastic about the subject.

At the age of seven Turner played Marta von Trapp, the second-youngest of Austria's famous family of singing Nazi-dodgers. Like Hall, she found her fame became a burden to her career rather than a help, and she gave up acting in her mid-20s, when she became pregnant with her first daughter. Like the Potter children, she was famous as one of a group, which means there's always her co-stars' memoirs to look forward to.

"Kym Karath [Gretl von Trapp\] and I used to butt heads quite a lot," she says, "because we were pretty close in age and her mother was maybe more of a Hollywood mother than my mom was. Charmian [Carr, who played Liesl von Trapp\] brought this out in a book she wrote recently, saying I shoved Kym off the stage that we were rehearsing on. I don't remember doing it, but she says I did."

Some child actors manage to stay in movies as adults, sometimes even topping their early achievements. Sean Astin, who played Mikey in The Goonies, will now be remembered for his role as Sam in The Lord Of The Rings. Harry Potter, however, may prove harder than The Goonies to leave behind.

Justin Henry shot to fame, aged eight, as the little boy in Kramer Vs Kramer, for which he was nominated as best supporting actor in the 1980 Academy awards, making him the youngest ever Oscar nominee. After taking time out to go to college, Henry, now 33, returned to acting and has continued working ever since. He describes Kramer Vs Kramer as a purely positive experience. Does it still come up at every audition? "Yeah, it does, and that sucks," he says. "That's tough, because for a while people expected the stars and the moon every time I came in the room, and sometimes they didn't get it. I think casting agents look at it like, oh, there goes that one."

Adolescence, where the Potter children now find themselves, was particularly tough, as Henry was still working a lot. "I'd be gone for three or four months here or there, and it was difficult, because I'd never be able to find a real core group of friends until I was about 15. A lot of kids couldn't really relate to me, and I had trouble relating to other kids."

At some point the decision about whether to stay in acting has to be faced. "I struggled with it, yeah," admits Henry. "When I was 18, 19, I didn't really know what I wanted to do with my life. And I did try to create my own identity outside of my acting, because I wanted to see what life was, not to be the child actor . . . but to just be Justin."

As for Jake Lloyd, he left acting at 10. Now 15, he's more interested in writing and photography. But not everybody in his school has forgotten Star Wars. "I get a lot of, hey, there goes Anakin. The most annoying thing kids have ever done is make light-sabre noises. And that's the only time I've really gotten angry. But then again, nothing makes you look more stupid than going 'Wwwhomh' behind someone else's back." ...

Harry Potter And The Prisoner Of Azkaban is on general release