POSEURS' POLO IN MANHATTAN-ON-SEA: Summer in New York is a season that only tourists admit they've seen. As far back as October, every New Yorker with any social pretensions at all hustles to find the most advantageous summer retreat possible, whether by renting a share with other up-and- comers, or by sidling up to friends with creaking family summer houses. When a Manhattanite ends up in August without a pied-a-mer, his or her only chance of avoiding shame is to get away at weekends. People who can't manage that don't answer the phone after sundown on Friday. On Monday, back at work, they will pretend they have been to the Hamptons.

"The Hamptons" is a snooty sobriquet for the south shore of Long Island, a charm bracelet of old New England towns and country clubs stretched along a sandy beach. To get there, people take the Hamptons Jitney - a snooty sobriquet for a bus - or the Long Island Railroad, a quaintly clattering train. Once, the Hamptons was the sort of place you would find the kind of people who didn't want to be found; austere blue-blooded Yankees. But now it's a grab-bag of Hollywood stars and studio execs, New York publishing bigwigs, rockstars (Sting, Billy Joel) club-promoters, dubious Franco- Italian royalty, and cagey arrivistes. This weekend, with the first match in the Hamptons Cup polo series, is the most unmissable of all. On a broad expanse of green, under white marquees, 300 women with cream-lacquered nails, Chanel bags, and short A-line frocks natter, smoking cigars (the summer's dernier cri), amid 300 men in rumpled cotton. The tablecloths flutter in the sea and meadow breeze, weighed down by gin, vodka and Pimms ... and a mammoth Mercedes-Benz silver star. In the Hamptons, all revelry comes with a sponsor.

On the field, burly foreign men and American super-moguls thump past on fine-tuned steeds. The men wear red shirts if they're Revlon's team, blue shirts if they're Sotheby's - but no one watches them. Who will win? No one cares. After all, the fans have not come to see the play; they have come to see each other.

And then, the Event happens. Actor Tommy Lee Jones arrives. Flashbulbs explode, prompting an explosion of toothy smiles. Someone murmurs that Salman Rushdie is there, and suddenly every man with a beard finds himself thronged. The crowd strolls alertly; everyone searches for someone they think might be camera-bait. What has brought these people here? It cannot be love of polo. What tradition are they emulating? Ralph Lauren's? They are not, in any case, emulating the real Hamptons people, the aborigines who do not want to be photographed, and don't like polo. One of these, a man who owns the serene, hilly estate that abuts the polo grounds, is suing (unsuccessfully) to get the polo crowd to remove themselves from his line of vision. Only one rallying cry this weekend succeeded in distracting anyone from the relentless pursuit of people-watching; and that was the word: Diana. Was, or wasn't the Princess of Wales coming to stay in Southampton for a few weeks, heirs in tow? The wases were more popular. "She's my absolute idol," a writer for a sun-spangled society magazine gushed. "When she wore her necklace as a headband, I did the same thing!" In pricey boutiques along the cobbled walks of old Southampton, clothiers squabbled over choice Di titbits. "The embassy says she's coming," one said knowingly. "The police won't confirm!" the other retorted - and then a woman who had been inspecting a necklace murmured that she happened to know the man who was renting his place to the princess - and named him. All conversation faded to a delighted hush. Would she make it in time for the next Hamptons Cup match, they wondered? And could they get tickets?