This isn’t a Girl Scout camp,” overseer Mr Sir tells new recruits at Camp Green Lake, the grim “facility” for young offenders where Louis Sachar’s bestselling novel Holes is set.

When the young cast turned up to film Holes in the California desert, they knew he meant it. They started with two weeks training to prepare them for the rigours of digging in temperatures of up to 50 LESS THAN C. In the story, Sachar’s young inmates have to dig a hole in the desert four feet deep and four feet wide every day, in theory to reform their characters but in reality driven by the secret agenda of the evil Warden (Sigourney Weaver in the film). The crew dug 500 holes and made 900 digitally (try counting them in the stunning opening shot) but the actors had to pick up a shovel in all the scenes that required it.

“They had to be able to dig as if it was second nature to them, and to bond in the way that the kids in the film bond,” says director Andrew Davis.

“They had to know what exhaustion felt like so that when we shot scenes out of sequence, they could walk home exhausted.”

Davis and his team visited young offenders’ institutions to prepare for filming. “Camp Green Lake is not based on a real environment, but the tensions in the group and the hierarchical positioning of the boys by each other are real,” he says. “What is touching about the story is the way in which it’s possible for them to be mean to each other but also kind.”

Shia LaBoeuf, who plays Camp Green Lake’s new recruit Stanley Yelnats, joined the training camp when the actors who played his teammates in “D Tent” were already established. “He had to be the new kid, which was appropriate. You see all the stages in the film of Stanley being accepted by the gang and being given his gang name, Caveman.”

Sachar’s novel, a National Association for the Teaching of English and DfES recommended read for key stage 3, weaves together three stories. In 18th-century Latvia, Stanley’s “no-good-dirty-rotten-pig-stealing-great-great-grandfatherensures that the family is “cursed for all eternity” by a fortune-teller, Madame Zeroni (a wonderful cameo role for Eartha Kitt).

The central story, set at Green Lake in the Old West, when there was still a lake, sees the sweet schoolteacher Miss Katherine transformed into the outlaw Kissin’ Kate Barlow after her black lover, Sam the onion-grower, is killed by racists.

In the present day, Stanley inherits the family curse from his father, a failed inventor, when he is wrongly convicted of stealing a baseball star’s shoe and sent to Camp Green Lake. The story, rich in curses, counter-curses, mysteries and coincidences, required three films in one.

Davis is best known for action thrillers including The Fugitive, Collateral Damage and A Perfect Murder, and admits that he had fun filming the Kissin’

Kate shoot-out sequences. He also relished the comedy that laces the tale of punishment and redemption.

Jon Voight and Tim Blake Nelson, as the Warden’s sidekicks, have built on their roles as Mr Sir and the creepy camp counsellor Mr Pendanski: like the Warden, they’re after Kissin’ Kate’s long-buried loot. “The cast has been an absolute dream,” Davis says.

As in the book, Stanley takes the first step to lift the curse when he starts teaching the youngest inmate, Zero, to read. “Stanley, like many children, has been parenting his parents, and you can see the responsibility for generations of mistakes on his shoulders. But because he’s able to be kind, things start to change.”

Holes is on general release from October 24 (PG)Louis Sachar’s novel is published by Bloomsbury Children’s books and Collins Cascades