Either of the boys, he believes, is at least the equal of Jodie Foster, who was 12 when Parker cast her in his first film, Bugsy Malone. "Their understanding of what to do is uncanny," he adds. "After three months I don't have to tell them anything. The key thing is not to talk to them as kids. I talk to them like any other actor. And they understand. They are so sophisticated."
Sitting by a heater in one of the make-up rooms on the film set, Ciaran Owens seems unfazed by it all. "I just like messing about and it's been great fun," he says. "The part I'm playing is such a sad life, so it is sad and there are some moments people might cry at. But everyone has been really nice. Joe and Michael are dead-on, and Alan is great crack. We've had a lot of fun." The youngest of five sons, Ciaran is in sixth class at St Bridget's School in Killeshandra, Co Cavan. He may have been missing school for the three months he has spent working on Angela's Ashes but he hasn't been avoiding his lessons - he has a tutor on the set every day.
He had a small role in The Butcher Boy, which featured his brother, Eamonn, in a remarkable performance in the central role. Ciaran went on to play one of the children of the Anjelica Huston character in her film of Brendan O'Carroll's The Mammy, due out next year. And he plays a gypsy boy in the 18th-century adventure movie, Plunkett and Macleane, which was filmed in Prague and opens here in the spring. "It's a very small part," Ciaran says. "Blink and you'll miss me."
Coincidentally, one of the stars of Plunkett and Macleane is Robert Carlyle, who plays Frank's father in Angela's Ashes. Carlyle, the versatile Scottish actor who starred in Trainspotting, Carla's Song and The Full Monty, and played Hamish Macbeth on television, sits in his trailer and laughs off the old adage that actors should never work with children or animals.
"That's partly true - with the animals," he says. "This movie has about ten thousand and fifty kids! Kids are natural improvisers and that's my background, too, in working with Ken Loach. You never get the same take twice with kids."
He believes the Scottish and Irish cultures are very similar.
"My father came from a huge family of 13, and they went through some dire times in Glasgow in the 1930s. So it's very easy to relate to that. When I told people who knew the book that I was playing the father, they said, `Oh, he's a bastard'. But I felt it would be entirely wrong to paint him as the villain of the piece. He does some terrible things, and lets the family down again and again, and he has a major drink problem, but the bad guy is the society that allowed that extreme poverty to prevail." Robert Carlyle describes his co-star, Emily Watson, as a kindred spirit. "It's strange," he says. "We were paired together for two other films this year, neither of which happened. She is one of the finest actresses I ever worked with. Her concentration and her poise are quite beautiful. I learned a lot from her and I hope I've made a friend for a long time to come."
"Emily has become Angela. She's amazing," Alan Parker observes. "The way she prepares and separates herself from her character. She's such a surprising actress in the way she suggests doing certain things, and she's always right."
However deeply she immerses herself in her roles, Emily Watson seems to switch off effortlessly between takes. "Have you seen the pigs?" she asks, pointing to the open shed where two plump pigs, which are also between takes, lie snoozing on hay while a third feeds from the trough. Watson looks radiant and a good deal taller than one might imagine from her film appearances in Breaking the Waves, her film debut which earned her an Oscar nomination, and Jim Sheridan's The Boxer, which she filmed in Dublin last year. And she is being tipped as an Oscar contender in the spring, having been nominated for a Golden Globe last week for Hilary & Jackie, in which she plays the English cellist, Jacqueline du Pre, who died from multiple sclerosis in 1987 at the age of 42.
She lights up a cigarette, explaining that she only took up smoking for Angela's Ashes. "Angela smokes 40 Woodbines a day in the film," she says, "but I'm going to quit as soon as we finish shooting." I note that she is looking very convincingly pregnant for her next scene. "The coat is stuffed with cotton wool," she laughs. As for the many, mostly inexperienced youngsters who play Angela's children at different ages in the film, she, like Parker, talks about how much she will miss them after shooting ends. "They're just delightful," she says. "They're all very open and very fresh and very innocent." The fate of some of the McCourt children in the movie is likely to prove wrenching for cinema audiences when the film opens in the autumn. Three of the children die in the early stages of the film. "We open our story in New York, on the tenement set we built at Ardmore Studios," says Parker. "The baby daughter dies. Then we go to Limerick and the twins die, one after the other. And that's just in the first 15 minutes of the film. Normally, you would work up to scenes to like that."
The twins are played by Ben and Sam O'Gorman, who at just two years of age are following in a family tradition into the film business - their father, Brian and his father, Andy, run the highly successful Ormonde cinema complex in Stillorgan, Co Dublin. Working with such very young children requires a great deal of sensitivity, Parker says. "The scenes are so harrowing, and these are real children. And you have to take into consideration the concern of their parents. For all those scenes I used two cameras, to avoid the need to do more than one take of each scene."
Sometimes the most effective scenes happen by accident, Parker says. He cites a scene in a railway station, where the family is waiting in the hope of the unreliable father returning home for Christmas. "Young Alfie is a baby at this point in the story," says Parker, "and Emily is holding him. We had quite a big baby playing Alfie and after we finished one take, I asked Ciaran to give Emily a rest and to hold the baby for her.
"Suddenly I realised we had this very powerful image of this young boy holding his little baby brother in his arms and saying to his mother, `Dad's not coming home, he's drunk in England.' And I shot it that way instead."