They don't do obituaries for once-great restaurants. Just a poignant paragraph at the back of the news pages. 'Bailiffs have moved into the venue, which was a popular haunt with celebrities during the 1990s ...' wrote the London Evening Standard last October of the closure of Oliver Peyton's great West End pleasure dome, the Atlantic Bar & Grill. 'It once attracted the likes of Francis Ford Coppola, Ben Elton, Lenny Henry, Kate Moss, Madonna, Robert de Niro and Harvey Keitel. He opened the doors of the Atlantic on 14 April 1994 and before long it was considered the coolest place in town ...'

'The coolest place ...' It's hard-won, that title, and in the Nineties it seemed to change hands every time someone thought up a new move with a scallop. Oliver Peyton was a night-club owner who had a notion of injecting late-night celebrity glitz into the still embryonic world of smart, young London dining. Landing a 3am licence certainly helped. Thus the Atlantic's Art-Deco halls certainly became one of the coolest places for a good three mid-Nineties years - a time when the thesp-hack glamour axis was the province largely of private members' clubs. It was long enough to establish the Atlantic sufficiently so that, when celebrity moved on, as celebrity does, the restaurant survived. (The Atlantic's lease has now passed to Luke Johnson of Pizza Express, but Peyton still promises it will return within three years.)

The Atlantic's longevity was unusual: by the end of the Nineties, with central London in renaissance and money flooding into the high-end dining business, restaurants had a cool life often measured in months. The Pharmacy summed up the era. It was the offspring of the decade's cockiest PR man and its savviest artist - a mating that, at that peculiar time, made perfect sense. The idea for the Pharmacy was simple enough. Damien Hirst and Matthew Freud acquired a run-down Greek restaurant on the summit of Notting Hill. The artist installed a six-foot model of his own DNA and decked the walls with Dihydrocodeine packets and varicose-vein treatments; the PR got the backers and the celebrities in. Liam Carson of the Groucho Club looked after the kitchen and everything else.

No one you ever met actually ate there - no one did much eating then, anyway - but for a few months in 1998 it seemed that everyone had taken a seat on the pill-shaped bar stools and drunk a Cough Syrup cocktail beside - oh, probably John Malkovich, Tara Palmer-Tomkinson and Norman Lamont. Celebrity-fusion was a trademark of the successful cool restaurant. You had another drink and then you left, probably pocketing one of the pill-box-shaped ashtrays. A set of six of those plastic ashtrays fetched nearly £2,000 at Sotheby's in 2004.

Within nine months of its opening on New Year's Eve 1997, the Pharmacy had been sold by Freud and his backers to the Hartford Group, an investment company specialising in City-boy bars. But the Pharmacy had already peaked. By the end of 1999, it was history, in cool terms. Hirst lost patience with it when he found unpaid bar staff picketing the entrance. By the time the saga ended, Matthew Freud said: 'I have a group of people who I've made promise to that if I ever say I'm going to buy a restaurant again, they are to hold me against a wall and punch me very hard.'

In late 2000, the Hartford Group had to be rescued from near bankruptcy and Freud was removed from its board. Carson and Hirst were already long gone, and the burly bouncers who'd once manned the doors had disappeared. You could get any table you liked at the Pharmacy now. Celebrities? 'Jeremy Clarkson still loves it,' was the word in Notting Hill. And though the Pharmacy lingered embarrassingly on till 2003 - when Marks & Spencer took over the site - its shelf-life as cool restaurant turned out to have been, at most, two years - a very long time, for a cool restaurant that doesn't do good food. (Or any food at all, at times: so unreliable were the kitchens that Damien Hirst used to send out to Notting Hill's Pizza Express to feed grumpy customers.)

And that was probably the point. Celebrity - even the double-A grade that the Pharmacy entertained - will launch a restaurant, but it won't sustain it. 'It was unnatural. Good restaurants don't come with a brouhaha like that,' Liam Carson said after the debacle. 'The Ivy and Le Caprice don't have all that bullshit.' That of course is the trouble with a cool restaurant - when the celebrities move on, what are you left with?

'Celebrity is the downfall of our society,' states OIiver Peyton now. 'It stifles creativity, it is not a healthy dynamic for restaurants. I like Gordon, I like Jamie, and good luck to them, but ... if you're in the restaurant business and you're a celeb that's great: if you're not, you're fucked.' The stranglehold of celebrity - the backers who believe celebrity guests and celebrity chefs are a crucial ingredient in a successful high-end restaurant venture - has snuffed out the invention that London restaurants were showing five years ago. It's got backers scared. The result, says Peyton, is Identikit cuisine and design - 'Bland! Microsoft how-to-open-a-restaurant-software-package-fucking-bollocks! Ludicrous!'

And it is all about London. It was Peyton who took cool London to Manchester when he opened a version of his Mash restaurant there in 1996, but the city could never sustain the venture, and it closed in 2000. 'The London chattering classes believe everyone's more savvy about food, but, frankly, go down any British high street, any motorway caff, and you'll see there hasn't been a British food revolution. It's bollocks. The only thing that has changed is there's a better quality of food in this country now - until the late Nineties we were still sending a van to Paris twice a week for ingredients. But we've not become a food-loving nation: it's a metropolitan myth.'

Elizabeth Crompton-Batt is the PR master for Nobu and Hakkasan. She had a stalls seat through the rise and fall of the high-octane celebrity restaurant phenomenon - she got married on the day in 1987 that Marco Pierre White opened Harvey's. The husband - Alan Crompton-Batt - was the PR behind White, and swiftly became a legend of his own. Crompton-Batt brought a rock-and-roll formula (he was formerly manager of the Psychedelic Furs) to publicising what was then the staid and stuffy business of running restaurants.

'That's when this started,' says Elizabeth. 'It was when chefs started throwing journalists out of restaurants.' Alan used to boast about punching Jay Rayner, the Observer's food critic. One of Alan's creations, Nico Ladenis, famously flambéed a critical customer's money in front of him. Chefs began to emerge from the kitchen - it turned out that they were not the shy, plump obsessives we'd been told: they could talk, fight, shag supermodels and do prime-time TV.

Alan Crompton-Batt saw how the two types of celebrity could mix - he famously married MPW to Michael Caine, as backer for The Canteen in Chelsea Harbour. With Matthew Freud, Crompton-Batt showed how celebrity could make a success out of a burger joint by getting Michael Douglas and Sylvester Stallone along to the launch of Planet Hollywood. It was the greatest food PR coup of the early Nineties. In 1998 Marco Pierre White, post-Canteen, went on to launch a grand resto-bar directly above the Atlantic in Glasshouse Street (he called it the Titanic - it sank): a move designed to annoy Oliver Peyton, which it succeeded in doing. MPW was said at the time to own half of all London's top restaurants. One venture of these was Quo Vadis in Soho, a partnership with Damien Hirst - which thus establishes the family tree through to the last great cool restaurant, the Pharmacy.

'It peaked at the end of the Nineties,' says Elizabeth Crompton-Batt. 'So much has changed. A few years ago I used to get calls from people saying, "We've got the site, we've got the celebrity backers, and we're ready ..." And for a while that scene worked. But they weren't really restaurants ... Celebs come once for the free meal, let's face it.' But Nobu - which notably holds the long-term cool restaurant crown in both London and New York - hasn't suffered from having Robert de Niro as a primary backer? 'Yes, but people can see through a place that's only about celebrities. Something has to sustain the interest generated by celebrity - and at Nobu, in any restaurant, that has to be the food.'

Which is a relief. We talk through some of the grand enterprises of the late Nineties - the Pharmacy, of course, the Titanic, the Odeon at Piccadilly Circus, Isola (Peyton's brutalist glam venue in Knightsbridge, which he sold a year ago), Dakota, footballer Lee Chapman and actress Lesley Ash's Teatro. 'It's over. Partly it's that licences in London are harder to get, and partly it's that, for a certain kind of backer, it's not fashionable any more to own a restaurant. Maybe they all want to be contemporary art dealers.' Peyton agrees: 'Restaurant culture is changing all the time - it's totally different from how it was five years ago.' Central London has declined - the fact that economics have forced the eclectic businesses that used to thrive in Soho to the suburbs has changed the clientele. 'People don't like to get a taxi back into town to eat.'

Have we, the restaurant-goers, grown up? Are we more educated now about what good food is, and indeed of how restaurants are run - just as we're more cynical about celebrities? In their different ways, both Oliver Peyton and Elizabeth Crompton-Batt think it comes back down to the grub. 'People know their food now,' she says, 'in a way they didn't 10 years ago - they go to markets, they care about what they eat. People will now only pay the prices if they get the whole package: a beautiful interior, staff that look great. But most of all the service has to be slick and the food has to be good.'

The coolest restaurant I've ever been to was the Globe, when Fergus Henderson (now chef-proprietor of St John restaurant in Clerkenwell) did one-night-stand events there in the late Eighties. The venue was a grungy little shebeen with a sheet-metal door that existed, quasi-legally, off the Portobello Road. You'd push through a pack of North Ken gangsters and trustafarians and dealers to find a bench in the basement. Then you'd wait patiently to see what emerged from the cupboard under the stairs where Fergus cooked. I particularly remember a plate piled high with spiny black sea-urchins - unadorned and unopened. But that was of course cool chiefly in retrospect - a foodie's equivalent of seeing the Sex Pistols play the 100 Club in 1976. I swear I was there. But, that was a cool restaurant, not a celeb restaurant, an important distinction best explained by the rule: while some celebs will eat cool food, celeb restaurants must serve comfort food. It's no guarantee of success, but the stars won't come unless you're serving, oh: gazpacho, lobster spaghetti, wild mushroom pasta, Parma ham and watermelon, rack of lamb, poached cod, five-cheese ravioli, baked Alaska.

That's a random selection from the menu at Bette, a new, wannabe uber-cool, 75-seat joint in Manhattan's impeccably trendy west Chelsea. The chef, Tom Dimarzo has a perfect celeb-resto background in both rock'n'roll (drummer for Mink Deville) and Asian-fusion (chef at London's Vong). If you look at any Heritage Cool restaurant, from the Ivy to the Savoy Grill to New York's greatest, '21', you'll realise that invention is out. '21' - serving celebs since Prohibition - puts out more 'Traditional Caesar Salad' than any other dish. Cosy food is a formula that works - the most challenging dish on the menu at Bette is 'American White Surgeon [sic] Caviar in a baked potato with crème fraiche'. 'Well, I'm not going to serve my friends a pig's ear, or something, that's totally not cool,' says Amy Sacco, proprietor and 'conceptual designer' of Bette. She makes a face that says 'Yeee-urrgh!'

Sacco is so cool that, when she arrived 50 minutes after our lunch in her restaurant was due to start, I was the one who apologised for her lateness. 'Sorry!' I bleated before Amy Sacco, and thus - for the only moment in our time together - slightly threw the 6ft1in monument to blonde self-possession that she is. But she got over it, apologised delightfully - 'You know what Fashion Week is like!' - and invited me to the party she was throwing at her club, Bungalow 8, for Naomi Campbell that night.

Sacco opened Bette last summer as 'a place for me to hang with my friends'. We're not talking just any old muckers. In New York, the city that still holds the planetary title Capital of Cool, Sacco is (says Vanity Fair) 'Queen of the Night'. The Regine of the 21st century. Her life-story is about to be a TV mini-series made by Sarah Jessica Parker's production company. Her club is so cool that there's no VIP room. 'I don't need one - no one gets in who's not a VIP.'

But Sacco's new restaurant, Bette, is not cool. It ought to be: it has the comfortable food, a scary matt-black exterior and the coolest toilets I've ever seen in a restaurant, so refined they need a plaque attached to the wall to explain how to work them. It's so not cool that you can get into it. I rang on a Wednesday afternoon and was told I could have a table on Friday evening. At 5pm or 11pm - but that's still a table on party-night. On the Thursday lunchtime - in the middle of New York fashion week - when I met Sacco, Bette had eight people eating - 10 per cent of capacity. 'Ah - I haven't really done much work on the lunchtime opening,' she muttered.

But a lot of work has gone into Bette. There's the toilets and the purple sacking upholstery (Chanel - 'Karl loved it!'), the site-specific art and some five star PR. Food may open a restaurant, but PR opens a cool restaurant. Bette's has gone perfectly. Amy herself can get into a gossip column by posting a letter - and there's been a wave of adoring profiles, most of them headlined 'Queen of Clubs' or 'Evening Star'. In August New York Magazine had a feature on the Fifty Most Beautiful New Yorkers - five of them were 'spotted at Bette'. If 10 per cent of beautiful New Yorkers hang out in this restaurant, how come the barely filled tables here that I can see seem to feature no face-lifts at all. Indeed the two blokes in jeans near us look like the delivery guys getting a freebie - the cheddar, bacon and tomato sandwich.

I asked Rob Wyatt, who is a fashion photographer and commutes between Notting Hill and Manhattan almost weekly, what is really cool for the glossy mag crowd. 'Macelleria in the West Village. Pastis for lunch at weekends.' Bette he'd heard of but it hadn't registered. 'Restaurants don't last nearly as long in New York [it's said that 70 per cent of new ventures don't make it for a year] - everyone's so fickle. The midtown wealthy crowd will pack a place, but only for a few months. It takes just one reviewer saying "it's all over", and the crowd moves round the corner and the place dies. The most interesting thing in New York is that people seem to have got bored of restaurants. They've started inviting you around to their place for dinner. That's new.'

London is different. Celebrity restaurants - when they do hit the mark - can last much longer. And they are about privacy and a sense of being with your own kind - nowhere 'full of North Face anoraks and shopping bags', as Wyatt puts it, will cut it. 'At E&O [in Notting Hill's Blenheim Crescent] you'll get Kate Moss and her bloke drinking all day and getting no hassle from anyone.' Hence the rise of the private-members' club, a London phenomenon New York hasn't really taken up - from the Groucho to Milk and Honey, a fashion-gang eating and drinking place whose PR is so discreet it likes to pretend it's an urban myth.

The Wolseley on Piccadilly has good celebrity-fusion - literary types through to football players - and notably, for its prospects as a long-term cool venue, has behind it Jeremy King and Chris Corbin, the team that made the Ivy. And long-term is obviously where the money is. Will Ricker's E&O is four years old now, and showing no signs of decline. It replaced another long-runner, 192, which for all the Nineties served Notting Hill's celeb and media set with a menu so comfy no one I asked could remember a single item on it.

Of course, New York still comes first. In the Eighties, hard-wired networking restaurants like Le Cirque catered to a whole tribe - the Big Swinging Dicks of the financial boom and the culture they spawned, Jay McInerney through to Tom Wolfe. At the same time City boys in London still went for cottage pie and claret in smoky-ceilinged, wood-panelled gentlemen's diners once patronised by their fathers. Even today, Wyatt sees the London cool restaurants lifting quite shamelessly from their New York peers. 'There's a steak sandwich with fries at the Electric [the Notting Hill off-shoot of Soho House], which comes on a wooden board with a pewter tub to dunk the chips in - that's straight from Pastis.'

It isn't all over. 'There's always a desire for big restaurants, if the place is beautiful enough,' says Oliver Peyton, and while all of his Nineties ventures except Mash are currently dead or dark, he has the much-admired, 200-seat Inn The Park at St James's Park and in February he will open the 185 cover National Dining Rooms in the Sainsbury's wing at the National Gallery in London. 'They say it's the worst business in the world to be in,' he groans. 'But it's my business.'

High-end restaurateuring is as swift and painful a way of throwing away large sums of money as ocean yacht racing. But some investors still stubbornly resist the notion that the celeb-driven restaurant era is over. A notable debutante in London last summer was Nozomi, which took over a spot previously occupied by a pompous Italian on Knightsbridge's Beauchamp Place. The owner, a nightclub and chain-restaurant magnate called Marios Georgallides appeared to have hired front-of-house staff by blood-line rather than experience - there's a minor Italian prince and a polo-playing pal of Prince William called Jacobi Anstruther-Gough-Calthorpe. The theme is safely Euro-Jap and the menu includes black cod, naturally, edamame, crab shumai and what one reviewer called 'supermarket grade' sushi.

Nozomi had an opening party in June featuring Tara P-T, Sophie Anderton and Formula One's Eddie Jordan. The reviews, predictably, could have been used to strip wallpaper: 'The eating experience at Nozomi was as cold, depressing and scary as any I have had in a long time' - said Giles Coren. But reviews don't matter - though they did to the kitchen staff, whom Georgallides sacked en masse. What does matter is that when I rang on a Friday in January I could get a table for six people for that evening.

Georgallides, when I spoke to him, insisted that the restaurant was full, except for Mondays ('We're new, we always accept more bookings than we can handle') and that his venture was going well. Why the celebrity launch party, I asked? 'They're friends - they would have come anyway.' And the titled front-of-house staff? 'They are young men who are friends and associates and want to make careers in marketing. They don't court celebrity.'

And the reviews? 'I see the critics as bullies - they don't stand up to be counted. Where are their qualifications? What do they know about Japanese food? It's risible - they vent their ire, but if it's you who's made the investment, put £2m or so in, all you can do is ride it, tell them to take a poke elsewhere. They should ask the people who really know what's going on - the investors.'

When Georgallides had calmed down a little I said, surely, having all those low-grade celebs attached to the venture was just asking for trouble from the crits - who are apt to get sarcastic. Had Georgallides learnt nothing from the fate of the Pharmacy? He told me how he once looked at taking over the Hartford Group, the ill-fated buyers of the Pharmacy back in 1999. 'But their problem is that they did rely on celebrities, having people who knew people. It doesn't work. In the end people come to you if the food's good. If the food's good and the operation's professional then the business lasts.' He said it. And then he invited me for lunch.