IF you're reading this over breakfast,spareathought for whoever is behind the shuttered doors of London's Earl'sCourtExhibition Centre right now. On the other side, clamouring to be let in, are several thousand teenage girls, drawn there by the promise of open auditions for the role of Lavender Brown in the next Harry Potter film.

It'sadreamroleandtheattendance today will reflect that. A similar screen test last year drew 15,000 teenagers and the lucky winner on that occasion was 18-year-oldKatieLeung,fromMotherwell.She queued for four hours, had a five-minute audition and now plays Harry's love interest, Cho Chang. No experience is necessary for the role of Lavender Brown but there is an age stipulation: 15 to 18 is the desired range which means the chosen girl could be a child, at least in the eyes of the law.

Beyond a little light snogging with Ron Weasley - nothing the average 15-year-old will be too bothered about - there is little in the Potter franchise that is likely to disturb a young actress (or her parents). But that isn't always the case where child actors are concerned.TuneintoRadioFour'sThe Archers omnibus today and you'll find a more troublesome storyline involving a far younger actor.

The newest addition to the cast of the long-running soap is six-year-old Matthew Rockett. Heplaysfour-year-oldRuairi, whose mother has died of cancer and who has been taken to live with his father,BrianAldridge,amarriedman whose wife and family are none too happy about the love child's arrival.

It's contentious stuff - doubly so because Matthew Rockett hasn't actually been told the details of the storyline. It was thought he would find it too upsetting to play the role of a boy whose mother has just died, his own being very much alive.

Insteadheisgivenlineswhichare recordedinhisDublinhomeandthen woven into the studio recording made with the other actors. It's the radio equivalent of blue screen acting and means the soap can have a child playing a child's role - these were always voiced by women in the past - while protecting that youngster from the true nature of the storyline.

At London's Royal Court Theatre tonight you'll find Bruce Norris's middle-class satire The Pain And The Itch. It stars Matthew Macfadyen as a rich businessman hosting a family dinner which descends into black farcewhenit'srevealedthathisyoung daughter, Kayla, has a troublesome vaginal infection. Incest is suspected - or at least strongly hinted at. Kayla is played by six-year-oldShannonKellyand,unlike Matthew Rockett, she can't deliver her lines from Dublin. She is there, on stage, and has to engage with material deemed so objectionable by one US theatre that it refused to put on the play.

"Never work with animals or children", runs the old showbiz adage. Nobody pays it any attention, though, and indeed the films and television programmes which throw children into situations of a high emotional intensity seem more numerous than ever.

Shona Auerbach has more reason than most to heed those words, having made her name creating television adverts featuring childrenand,latterlyasthedirectorof Scottish film Dear Frankie. It featured Emily Mortimer and Gerard Butler but the star turnwasnine-year-oldJackMcElhone playing the titular Frankie, a deaf boy who thinks his father is away at sea when in fact heisanabusivedrunkfromwhom Frankie's mother has fled.

"Children don't work in the same way as adultactors,"saysAuerbach."Their instincts are much more apparent and they work off those instincts, so you have to direct them differently. They don't think too hard unless they've gone to theatre school andthey'vebeenencouragedtothink about how they're delivering their lines."

Emotional and social intelligence are vital, however, as is theabilitytodistinguish between what is real and what is role play. Those are the ingredients that make a successful child actor, ingredients Auerbach says she found in McElhone. "I never felt I needed to talk to Jack like he was a child. There was many a time he turned to me and said, I'm not sure if Frankie would do that'. So he was smart enough to understand the part he was playing and he could understand that he was playing a part. He understood the separation of performance from real life and I think that's a really important point."

McElhone was chaperoned on set by his mother - his father is Texas guitarist Johnny McElhone - and had some previous acting experience,havingappearedinYoung Adam. He turned 10 during the shoot which meant he could work more hours and that madeagreatdifferencetoAuerbach's shooting schedule. But even aged 10 those hours were still strictly limited.

Employment legislation states that young actors cannot work more than two hours on a school day. Technically nobody under 14 is allowed to work, though local authority dispensationsareavailable,which essentially means regulations can be waived.

The actors' union Equity does not accept membershipapplicationsfromactors younger than 16 because of the legal difficulties surrounding contracts. Neither does it have an official set of guidelines governing the use of young actors. However, both of those policies are currently under review.

On commercials Auerbach has shot, the rules are even tighter. She recently completed a Childline advert for the National Society for the Prevention of Cruelty to Children (NSPCC). In it, a young girl who is suffering abuse at the hands of someone in her family comes home from school and goes up to her room. The actress was 10 years old.

"The girl and her mother knew the script and were absolutely happy to do it," says Auerbach, "but I wasn't allowed to talk to the girl about it the issue of abuse. I couldn't be seen to be upsetting a child. I was never allowed to let her feel sad."

In other words Auerbach couldn't make the girl feel unhappy, she could only make her look as if she felt unhappy. Moreover she was filmed by the NSPCC throughout themakingoftheadverttoensureher compliance with these stipulations. "It was really hard," she says. "We had to approach it from a different angle. The sadness in her face had to come from somewhere else. You had to get a sense of sadness through the eyes so for example I would ask her to concentrate really hard on something that had happened at school that day."

However, there are many other cases in which child actors are asked to grapple with roles which require a full understanding of what'shappeningtotheircharacters. Earlier this year, the Sundance Film Festival was mired in controversy when it screened the premiere of Hounddog, a film set in America's Deep South in the 1950s and starring 12-year-old Dakota Fanning as a precocious and troubled pre-teen. Fanning has one nude scene and several more where she is dressed only in her underwear. But the most contentious of all - and the one which had the American family values movement out in force - is a scene in which she is raped.

HounddogdirectorDeborahKampmeier's script states: "There is no nudity or explicit violence in this scene. All nudity and violence is implied." We know this because the script was later leaked to website The Smoking Gun. We also know that Fanning's mother was present throughout the shoot and that the whole scene was never shot from start to finish. Instead it was assembled incrementally and then edited together.

Fanning'sagent,CindyOsbrink,has worked with the actress since she was five (like many in Hollywood, Fanning started young). Osbrink recently told US film magazinePremierethattherolewas "somethingthatreallychallengedFanning's talent. Hounddog was one of the best experiences of her life".

Kampmeier,meanwhile,deniesthatFanningwas even exposed to a simulation of rape. Yet Fanning must have read the script so there can have been no hiding from her the fact that her character undergoes a serious sexual assault. Predictably, Hounddog has yet to find a distributor.

Noneofthisseemstohaveaffected Fanning'sdesiretotacklecontroversial roles: she is now rumoured to be in the running for the part of Susie Salmon in the film adaptation of Alice Sebold's novel The LovelyBones.Fourteen-year-oldSusie narrates the story from heaven, looking down on her grieving family after she has been raped and murdered by a neighbour and her body hidden. Lord Of The Rings director Peter Jackson will make the film, which is due for release next year.

Thenovelisn'taneasyreadandit certainly won't be an easy film to watch. So what effect might it have on the young actress who lands the role of Susie?

Perhaps Brooke Shields would have some illuminating comments on that subject. In 1978, aged 12, she played an 11-year-old prostitutecalledVioletinLouisMalle's historicalfilmPrettyBaby.Therewere many nude scenes. Susan Sarandon played the motherwhoauctionsoffherdaughter's virginity, and legend has it the actress gave Shields a thong to wear on set, uneasy perhaps at the child's nakedness.

Discussing the film with the veteran critic Philip French in 1993, Malle recalled that thestudiohadhadextrememisgivings about Pretty Baby and almost pulled out at the last minute. Malle auditioned several girls for the role of Violet but always came back to Shields. Still, he said: "It was a difficultparttocast.Ihadalotofmixed thoughts about asking a child to go through these very disturbing scenes. I felt I had a moral responsibility."

His decision to cast Shields eventually came down to the fact that she had already been working as a child actor for more than a decade. "She had been exposed at an early age as a model - I'm not saying it's the same thing, but she had been selling her body all those years. I think she was mentally strong enough to handle the part Because of the complex nature of her family life in those days she was tough as nails."

Interestingly, Malle's screenplay called for a great deal of vulnerability from the actress chosen to play Violet; Shields simply didn't have that and he had to rewrite his script accordingly. Tough as nails indeed.

Shields's then manager was her mother, Teri. She once said of her daughter: "I think Brooke is sort of like a work of art. And like any beautiful painting, I think the world should enjoy Brooke and view her." Shields fired her in 1995 and later referred to her as "a pitbull".

Des Hamilton knows all about pushy parents, having worked as a casting director on some of the biggest Scottish films of the last decade,includingYoungAdam,Dear Frankie and this year's Edinburgh International Film Festival opener, Hallam Foe.

Hehascasteveryonefromnewborn babies to pensioners and is aware of the qualitiesachildactorneeds-andthe perils they can face.

"The casting director is the first point of contact for a young actor and that's very important," he says. "You can't just disappear afterwards."

It's up to the casting director to form a relationshipwiththeactorand,importantly, the actor's parents or guardian. That relationship will continue even into filming,hesays.Mostlyhisexperienceof working with the child actors' families is good, however, and he too is full of praise for Jack McElhone.

What happens, though, when even the filming is over? What responsibilities do film-makers feel towards their young cast members when the publicity circus begins orwhenthemoviestartsatourofthe world's film festival circuit? "A child does need someone to protect them, an agent or publicist or someone like that," says Shona Auerbach."We'veallseenithappento Hollywood child actors, how much success has coloured their whole lives. But in our case I think Jack was very cool in the beginning, and when it came to all the publicity he just took it in his stride."

THAT publicity included a triptoCannesin2004, whereDearFrankiewas showing in the Un Certain Regardstrand.ForJack McElhone, it will have been fun but not every young star has such fond memories of the world's most famous film festival.

Bjorn Andresen was 15 when he played the beautiful Tadzio in Death In Venice, Luchino Visconti's take on Thomas Mann's infamous novel. Andresen plays a holidaying boy who becomes an object of desire for an elderly male tourist, played by Dirk Bogarde. Andresen had just turned 16 when he found himself at Cannes, dragged along to a gay club by the bisexual Visconti where he was treated as "a nice meaty dish". The experience scarred him.

Andresen was a child actor in Sweden, having been pushed into commercials by his grandmother who would apply on his behalf to adverts in the Swedish press. If they'd been auditioning for Harry Potter in Stockholm in the late 1960s, it's safe to say he would have been there - a cautionary tale, perhaps, for the thousands queuing in London today. Matthew Rockett and Jack McElhone have fared well within the industryandnodoubtthefutureLavender Brown will too. But not everyone in the film industry wears kid gloves.