As he quietly turned 44 earlier this year, still single, childless and with signs of wear showing on his finely sculpted chops, Hugh Grant had at least two reasons to be cheerful. His big new movie, Bridget Jones: The Edge of Reason was soon to open, and, four years after his split from Elizabeth Hurley, the actor seemed, once more, to have found love.

Behind the dithering exterior, Hugh Grant is a ruminative soul, and his romance with the heiress Jemima Khan, 30, has given him plenty to ruminate about. Of all the women he might have fallen for it is hard to think of one more certain to attract the kind of attention that he professes to loathe.

When they were first seen out together, all talk of an affair was denied. They were merely old friends, and when Jemima's marriage to the former Pakistan cricket captain Imran Khan broke up, Hugh was there to lend a helping hand. The hand was soon seen caressing Jemima's shapely bottom as the couple frolicked in the sapphire waters of the Riviera. Now the romance is out in the open, the movie is out in the cinemas, and Hugh Mungo Grant, cloaked in a grey pallor of melancholy, says he is out of showbusiness.

"This is the last film I will ever do," he declared at the film's London premiere last week. "There's not much excitement any more. I just lost interest, to tell the truth. I don't return my agent's calls. I don't read scripts very much. I was never a very committed actor. Now I can stop."

Asked, bluntly, what his life was like, he replied with a short expletive. Suffering for your art is one thing, but jacking in the job of being Britain's biggest box-office star suggests that Grant's troubles go beyond angst or boredom. At the post-premiere party, he hid himself away behind a human wall of hangers-on, and lashed out churlishly at an invited photographer. Is he serious about quitting? As Colin Firth, his Bridget Jones co-star, says: "We can only hope and pray."

The elements of Hugh Grant's malaise are many, and most of them can be observed in what passes for his personality. Ten years after he became a national treasure with Four Weddings and a Funeral, the actor seems to have no more sense of what he really wants to be than we have of who he really is. What can be said with some certainty is that his charm is diminishing, his self-regard is expanding, and his chat-up lines, never greatly indebted to Donne or Byron, are sadder than ever.

"Maybe I am, in some way, obnoxious," he has said. "That's all I can guess at. I must say, I watch myself doing interviews on TV and I think, 'Yeah, that is sick-making'."

As middle age descends upon him, Grant's ambitions as an actor may have been realised. But now another aspiration - not, in itself, an unworthy one - consumes him. Born into a close family, he has made no secret of his desire to marry, settle down and have children, or of the kind of woman he would consider as a suitable partner. Beauty matters to him, as - being a man of some intellect - do brains; but if Hugh has a core susceptibility, it is for what you might call class.

A former girlfriend, Jody Tresidder, recalls Hugh complaining to her that he was mocked at Latymer, the London private school that he attended, for having had a father "who sold carpets". Ever since, Grant has demonstrated an unusual reverence for money and good breeding.

With Elizabeth Hurley, the daughter of an Army officer, he believed he was on the right track. The pair met as relative unknowns in 1987 and stayed together for almost 15 years. While you wouldn't say Elizabeth lacks pedigree, Ms Khan hails from an entirely different league. The daughter of the late billionaire businessman Sir James Goldsmith and his exuberantly aristocratic mistress - later wife - Lady Annabel Vane-Tempest-Stewart, Jemima was reared amid wealth and privilege of an almost surreal order.

"At first," says a friend of Jemima's, "she wasn't that interested in him, but Hugh was extraordinarily persistent. She had had a very difficult time in the last year of her marriage to Imran, and to suddenly have all this attention was very nice for her. Now she is in love with him."

Even as a student, Hugh was keenly aware that there was a richer, more refined world than the one he belonged to. An Oxford contemporary recalls him dressing in a tweed jacket and brogues, to hold traditional tea parties where egg and cress and cucumber sandwiches and Earl Grey tea were served from college crockery. "Here were all the Old Etonians pretending that they hadn't been to Eton, because, of course, it wasn't quite the slightest bit cool to have done so. And here was Hugh, acting as though he had been there when he hadn't. It was all pretty confusing."

"Hugh lives his life as though he is in an Evelyn Waugh novel," one of the actor's friends has said. "He is fascinated by the aristocracy." And it is true that with his bumbling mannerisms, foppish affectations and polished stammer he could have wandered straight off the pages of Brideshead Revisited.

Class is a particularly English obsession, and it is, perhaps, unfair to expect an actor as essentially English as Grant to be immune from its influence. Yet the impression Grant gives of a man desperately unhappy in his own skin is one that may be strangely familiar to him. His father, James, dreamed throughout a respectable, if unelectrifying, career as an executive carpet salesman, of being a watercolourist. With his wife, Fynvola, he raised his family in modest comfort in Chiswick, west London, where Hugh, the younger of two sons, grew up convinced - or, perhaps, persuaded - of his specialness.

From the start he had charm, and good looks, and girls adored him. Mallary Galb, a pupil at the neighbouring Godolphin girls school, recalls: "He was by far the most beautiful boy around, and I can still remember the intense feeling of excitement when we first danced and kissed at a party. I got kicked out of some silly girls' gang because they were jealous. But I didn't care."

At Oxford, mesmerised by the leisurely decadence of the upper-class set, he joined the notorious Piers Gaveston Society, an organisation largely dedicated to the pursuit of extreme drinking and sexual ambiguity. Unsure of what to do after university, Hugh opted to try his hand at acting. He played in provincial rep, scored occasional television roles, and in 1986, landed a part in James Ivory's Maurice, a film adaptation of E M Forster's gay-themed novel, which won him favourable reviews. The following year, on the set of the little-remembered Rowing with the Wind, he met Elizabeth Hurley.

Four Weddings made both their careers. Even though Elizabeth wasn't in it. He played the part and she wore The Dress, and they struggled on even after Hugh was caught in a car with a $40-a-trick Los Angeles prostitute. Since their break-up few women appear - until Jemima - to have figured closely in his life. One who did was Kasia Komorowicz, a 30-year-old business consultant. She describes a man seemingly plagued by self-doubt, and a profound reluctance to trust anyone.

He told her, she says, that he longed to settle down, to marry and have children, yet lacked the belief that he could make it work. "He seemed emotionally confused and was dissatisfied with his career, saying it wasn't creative enough. Once I asked him if he was in love, and he said: 'No, I'm never in love.' "