Debutant Martin Compston plays Liam, a boy who takes to dealing drugs to raise enough money to buy his imprisoned mother a caravan on her release from prison.

Compston - a footballer for Scottish Third Division side Greenock Morton - was found by Loach after three months of auditioning up to 300 hopefuls.

My experience of real life was my research

Martin Compston

Loach is a firm favourite at Cannes, with many European audiences taking to his gritty portrayals of urban life more than British cinemagoers.

And he has already won universal acclaim from critics at Cannes for the performances he drew from the untrained teenage actors making their debuts.

But critics were relieved that Loach added English subtitles for the Cannes screening out of fear that the thick Scottish accents would be incomprehensible to some.

"We had subtitles out of respect for the audience here," he told reporters after the screening.

Main ambition

There has already been speculation Loach's effort is among the frontrunners for the prestigious Palme d'Or Award.

Grinning from ear to ear at the press conference, Compston could not believe his luck to be at the world's most glamorous film festival - but he still confessed his main ambition was to play football for a living.

Violence abounds in Loach's grim world of jobless youngsters facing a future without hope on a Scottish housing estate.

Compston was found after a three-month search

"I know so many people like that. It wasn't acting," Compston said of his searingly realistic portrayal.

"I am not an actor. That is why Ken picked me. He moulded me and I gave it my best shot.

"My experience of real life was my research."

And Loach clearly watched in fascination as the teenagers grew in the roles.

"We were living off what they did instinctively," he said.

"They helped to reveal the characters."

Loach, a master of "kitchen sink" movies, first came to prominence in the 1960s with the powerful TV film Cathy Come Home, which made a generation in Britain aware of the corrosive effect of homelessness.

On the silver screen, Kes - his 1969 tale of a young boy and his falcon - was hailed a masterpiece.