We're mad about the boys

Sitting before Hugh Grant is a jumbo-sized chocolate penis displayed to advantage inside its Cellophane packaging.

"The penis," says Hugh, with the air of someone who has a genuinely insightful contribution to make to the creative process, "don't you think it should come out of the box?"

It is a moment I shall always treasure. Last summer I was granted access to the Shepperton set of Grant's new movie, About a Boy, based on Nick Hornby's novel of the same name and opening in April. Grant plays Will, an emotionally retarded, commitment-phobic thirtysomething who makes friends with a lonely, nerdy 12-year-old called Marcus (Nicholas Hoult).

The day I visited the set, the crew were shooting an excruciating Christmas party scene during which the above penis is presented to Marcus's mother (the wonderful Toni Collette, playing a neurotic depressive). I could see the back of Grant's head, but the thrill soon wore off. As anyone who has been on a film set knows, movie-making is extremely boring to watch; and I knew there wasn't going to be any snogging because Rachel Weisz, who plays the love interest, was not on set that day.

The end result is anything but boring, however, if early critical word of mouth is anything to go by, although boredom, along with disaffection, ennui, guilt, resentment and a wry sense of irony are key emotions in Hornby's work. About a Boy is adapted and directed by the American brothers Paul and Chris Weitz, the writing/directing team behind American Pie and Down to Earth. The Weitzes commercial instincts are unerring (Down to Earth made $65 million at the American box-office alone), but they have so far failed to please the critics. On the face of it, the production company, Working Title, may seem to have made a surprising choice for a downbeat Britflick set in Clerkenwell and peopled by single mothers, delinquent teenagers and a screwed-up serial bastard. Or perhaps, and on reflection this seems more likely, the Weitzes are just what is needed.

In person the Weitz brothers are very far from brash or cigar-chomping. Well-bred East Coast intellectuals would be a more accurate description, though their family has deep roots in Hollywood. Their grandfather, Paul Kohner, was agent to John Huston, Ingmar Bergman and Billy Wilder, and their grandmother was the Mexican silent movie star Lupita Tovar; their father is the fashion designer and writer John Weitz, and their mother is the Academy award-nominated actress Susan Kohner. When they first started working on American Pie, their father was appalled. "He kept saying¸'Well, doesn't Merchant Ivory need someone to write their films?' and we did American Pie instead of Howards End II or whatever it may have been. But our dad is proud of us anyway," says Chris. "We try to bring the Merchant Ivory tone to any sex film that we do, though," jokes Paul.

So how did they get from the broad humour of American Pie to the darker tones of About a Boy? "My brother and I want to be able to make all sorts of films and, hopefully, have a career in which we can move between genres in a way a lot of the directors we admire - Billy Wilder, Howard Hawkes, Akira Kurosawa - could do," says Chris. "After Down to Earth we were looking for a Wilder-esque project, something which, rather like Wilder's The Apartment or The Graduate, was cynical about people in general but hopeful about specific people."

Hornby's book was just what they had in mind. Will lives off a private income in a groovy loft apartment kitted out with stainless steel gadgets; his girlfriends are fleeting and his main leisure activity is shopping for CDs and clothes. It's the world according to GQ, yet it's clear that Will surrounds himself with objects in order to fend off the world and distract himself from his own unhappiness. "I'm interested in movies about lost people," says Chris. "I like the idea of starting off with a distasteful character and breaking him down." It helps that Hornby's book is already very cinematic, he continues. "The character's interior life comes out in dialogue and they are largely reticent or embarrassed about their emotions. In fact, in terms of dialogue, the book is a better screenplay than many I've read."

Grant had wanted to play the part ever since reading the book, and was on board long before the Weitzes. About a Boy certainly allows him to "move on" as an actor. The floppy hair has been shorn to reveal the face of an older, craggier, more watchful sex God, and the trademark drawl has been replaced with nondescript Estuary English. "In the movie Hugh shows another side of his nature behind the charm and the immense likeability and charisma, though they are very real and actual qualities," says Chris. "And I think he does identify with the character of Will. I don't want to suggest that he's a depressive, but he's often said that he's the kind of guy who has to have the TV on or the radio playing. He is one of those people who need to divert themselves from their own lives in rather hectic ways."

The brothers are fittingly appreciative of their London crew. "There's this wonderful European sense that working on a movie should be fun as well as rewarding," says Chris. "Peo-ple have a good time. We've already had a halfway-through party which got pretty ugly. Many people got very drunk." His favourite aspect of shooting in London, though, is that he gets to be called "the Guvnor". "I do like that," he confesses, with a boyish grin of pure, 24-carat American charm.