There was a moment back there in the mid-Eighties when eating turned into a competitive metropolitan sport. It wasn't so much what you ate. Or with whom. But precisely where you ate it that mattered. At a certain time, for a certain breed of cosmopolitan, table nine at Le Caprice was pretty much the pinnacle of social achievement. In the age of hierarchical, must-get-a-reservation dining, it said, simply, that you'd arrived.

In many respects, it still does. Twenty-five years on, the place continues to bristle with the brokering of business contracts and signing of book deals. As chef-director Mark Hix puts it, 'At Le Caprice, you can have a pen in one hand and a fork in the other. Just try doing that at a two-starred Michelin restaurant. We get a lot of power lunches here.'

There are a lot of power people too. On any given night, if you possess anything as recherché as a reservation, you might dine with rock'n'roll, royalty, or a cross-pollination of the two, with a few moguls and multi-millionaires thrown in for added bulk. Vogue's editor may be doing chopped steak, Nigella Lawson could be forking into a caesar salad, you might well trip over Bryan Ferry or Liz Hurley en route to the door. Michael Winner insists on table seven (as he says, 'I don't go to restaurants. I go to tables'). Apparently, Ned Sherrin always decides what he's going to have in the taxi on the way there. When designer Matthew Williamson dined here with Madonna recently, he was so nervous that he had to walk around the block to get his bearings. A few weeks ago, Sharon Stone chose to leave her own London premiere of Basic Instinct 2 in favour of supper at Le Caprice. The restaurant was, of course, once a haunt of Princess Diana; today, it's a regular lunch date of Camilla's ('I come here all the time with my mother,' says Tom Parker Bowles. 'It's probably her favourite restaurant of all time').

While other renowned restaurants have traded on perfectionism (the Ramsays), experimentation (the Blumenthals) or on a thrilling celebrity clientele (the Nobus), Le Caprice has always been about people. 'We're not necessarily food-led,' says Hix, with a candour unlikely in a chef. 'It's about the package.'

That package is headed by the reassuringly expensive Bolivian maître d', Jesus Adorno-S - a man who knows everyone who is anyone and then some besides. Says one Caprice habitué: 'He knows your face, your tastes, your children's names and he'll keep a bottle of Bombay with your name on it behind the bar.' According to Jesus, 'Le Caprice is like a club - people come back again and again ... yes, I treat stars with reverence but it is the same reverence as I show anyone who comes here.'

If you do manage to nudge your way in, you'll discover that the food itself is comfortable rather than cool. Contrary to expectation, Le Caprice has never been extortionately priced, nor foolishly fashionable. Instead, it has always served precisely the kinds of things you'd put on a menu if you owned the joint. Eggs benedict, salmon fish cakes, steak tartare. Says Hix: 'Cooking is about what the customers want to eat, not what the chef wants the customers to eat.'

Yet they come for the air of the place as much as what's on their plates. Most regulars - there are many, many regulars - have their treasured Caprice moment. Sir Peter Blake remembers the night that Omar Sharif punched Ian Dury in the face: 'It wasn't until Ian was out cold on the floor that Sharif realised Ian was disabled. It was like being in an episode of Extras.' 'We were here on the night that Laurence Olivier celebrated his 80th birthday with Elizabeth Taylor, Liza Minnelli and Barbra Streisand,' recalls Blake's wife Chrissy. 'That was a bloody good night. At the end we stole Liz Taylor's wine glass with her lipstick on.' Tim Taylor - who romanced Lady Helen here - remembers 'coming in here in the mid-Eighties and having Sunday brunch at the bar. John Gielgud was sitting two places down. I remember feeling, "Yes, this is the place to be".'

Though Le Caprice is celebrating its 25th birthday this year - with a bash at the Serpentine Gallery, hosted, of course, by Jesus himself - in fact, the restaurant has existed, tucked behind the Ritz in Arlington Street, just off Piccadilly, since 1947. But it really found its legs in 1981 when it reopened under the stewardship of Chris Corbin (from Langan's Brasserie) and Jeremy King (of Joe Allen). The pair became the capital's patron saints of must-see dining during that decade of hairspray and Filofaxes, and later went on to buy the Ivy and transform it into the star-pot it is today.

In truth, Le Caprice hasn't changed much over its quarter century. The service is still impeccable. There's still the neon-blue scribble of the signage outside, the long bar, the black-and-white David Bailey portraits of Beaton and Nureyev, Polanski and Tate, Faithfull and Jagger lining the walls, the rectangular room done up in monochrome - a bit of a throwback, that. 'The design is everlasting,' says Hix. 'It's Pizza Express, really, isn't it?' With knobs on.

Today, you'll find Corbin and King over at the Wolseley on Piccadilly. Le Caprice and its sister restaurants in London's 'Holy Trinity' (the Ivy and J Sheekey) were sold, first to Luke Johnson's Belgo Group, and subsequently to retail entrepreneur Richard Caring, whose latest acquisition is Scott's of Mayfair, which reopens next month after a grand refurb. Caring's plan is to develop the profile of his new purchases. 'Above all they have names that no one else can emulate,' he says. 'I've bought restaurant brands and the world today is brands ... There will be a second Le Caprice in New York in a year's time and we are also looking at Moscow.'

But for now - and probably to the relief of most of the guests at the Serpentine - there's still only one Le Caprice. As I'm about to leave the party, I notice that there, in among the Angela Rippons, the Simon Callows and the Anne Robinsons, sandwiched between the money and the mavens, is Jeffrey Archer, a man for whom Le Caprice is more than simply a pleasing place to eat risotto nero. Le Caprice, you might recall, was name-checked in his alibi for that fateful night in September 1986 when his descent from frontline politics began. 'Table nine is also known as Jeffrey Archer's table,' confides Mark Hix. 'He came here for his first lunch as a free man.'

So why does Archer return, time and again, to the scene of the crime - or at least its very near neighbour? I trot over to find out. 'For the people,' he says ruminatively. 'I don't go to restaurants for the food, I go for the people.' With the help of Jesus, you see, even the fallen can be redeemed.

Le Caprice: 020 7629 2239; www.le-caprice.co.uk. For outside catering log onto urbancaprice.co.uk

Fishcakes - Le Caprice style

650g mashed potato

650g salmon fillet, poached

2 tbs tomato ketchup

2 tsp anchovy essence

3 tsp English mustard

salt and pepper

For the sauce:

1/2 litre strong fish stock

50g butter

30g flour

50ml white wine

250ml double cream

15g fresh sorrel, shredded

salt and pepper

1.5kg spinach, picked over, washed and dried

Mix together the potato, half the poached salmon, the ketchup, anchovy essence, mustard and seasoning until it is smooth. Flake the remaining salmon and fold in. Mould the mixture into eight round cakes and refrigerate. Bring the stock to the boil in a thick-bottomed pan. In another pan, melt the butter and stir in the flour. Cook slowly over a low heat for 30 seconds, then whisk the fish stock into the flour mixture.

Pour in the white wine and simmer for 30 minutes until the sauce has thickened. Add the cream and reduce sauce until it is of a thick pouring consistency, then add sorrel and season. Flour the fishcakes and fry until coloured on both sides. Wash the spinach, remove stalks, then drain. Heat a large saucepan over a medium flame, add the spinach, lightly season with salt and pepper and cover tightly with a lid. Cook for 3-4 minutes until the leaves are tender. Drain. Put some spinach on each plate, then a fishcake and sauce.