CANNES, France (Reuters) - Film festivals often throw up unexpected new talent and Katie Jarvis, the 17 year-old star of British director Andrea Arnold's "Fish Tank," in competition at Cannes, is the latest.
Discovered at Tilbury railway station, in Essex outside London, by a casting agent who overheard her having an argument with her boyfriend, Jarvis fit the part of the mouthy teenager Mia perfectly.
"She was giving him a bit of grief across the platform and she stood out," Arnold told a press conference after the film was screened.
Jarvis, who has just given birth, was not at Cannes but her performance has drawn praise in media ranging from Hollywood trade magazine Variety, which called it "mesmerizing" to the heavyweight French daily Le Monde, which called it "remarkable."
"Today, I'm starting to worry about her," Arnold told Reuters Television in an interview on Friday. "People are talking about her and I'm now thinking 'Oh Crikey' and I am worrying about what that means to her.
"It must seem strange because she's getting a lot of phone calls from us and I told her today to look on the Internet and she's very excited," she said.
"Fish Tank" conjures a peculiar mix of gritty authenticity and mystery from its setting, a nondescript area of scrapyards, housing estates and highway underpasses that cut through the wild and isolated country to the northeast of London.
But Jarvis's raw portrayal of a girl passing the days in aimless bouts of cider drinking and losing herself in lone sessions of hip hop dancing in an abandoned flat is at the heart of the film's wandering progress.
Mia spends much of the film trading insults with her mother, her younger sister, the other girls on the Essex housing estate where she lives and most of all, with her mother's dangerously charming new boyfriend Connor, played by Michael Fassbender.
Circling warily around the handsome newcomer and alternating between spitting abuse and uncertain enjoyment of the compliments Connor pays to her dancing, Katie is prey to a troubled mix of hostility and attraction.
Fassbender, a hit at Cannes last year as IRA militant Bobby Sands in Steve McQueen's "Hunger" and Kierston Wareing, who featured in Ken Loach's "It's a Free World" were both film veterans but for Jarvis the experience was entirely new.
"Part of me thought, it might not work, we might not get through it and she might not be able to do it," Arnold said. "But I like taking those kind of risks and she's quite a strong girl, she's quite resilient and I think that was paramount in her being able to get through it."
Arnold said her faith had been rewarded.
"She felt that she had achieved something," Arnold said. "She said she'd found she could do something in her life, she'd discovered something about herself."
"It could be a really, really positive thing for her. It's just that it is overwhelming."
Additional reporting by Cindy Martin, editing by Paul Casciato