He made his name with fashion-conscious restaurants like the Atlantic Bar and Grill and Coast, but with the opening of his pounds 3.8m flagship in Knightsbridge, restaurateur Oliver Peyton is hoping to provide an altogether more grown-up dining experience
Oliver Peyton is becoming more audacious and more adult. The Irish- born restaurateur's ventures (which include The Atlantic Bar and Grill, Mash, Mash and Air, and Coast) have usually been successful, even if they have perhaps felt a touch stylised and even ephemeral. But with Isola, his new Italian restaurant which opened this week in Knightsbridge, Peyton is trying to pull off the most difficult trick of all. "I want it to seem as if it has been open for ever," he says, "as if it is part of the local landscape."

Isola's pitch at longevity is to provide a US-style, banquette-and-booth power base for Knightsbridge big-business lunchers and discreet diners. It is moderne and retro, yet timeless enough to seem stable, rather than here-today, gone-tomorrow fashionable. The high concept is "power dining", inspired by the great, post-war restaurant culture in America, and even the UK's prestige-led catering boom of the Eighties and Nineties. Yet, with Isola, Peyton hopes to avoid the faddishness which has beset 20th- century British restaurant culture.

His most obvious reference is New York's Four Seasons restaurant (designed by Philip Johnson); indeed, his working rubric is "Albert Speer meets the Four Seasons". Peyton has always emphasised the design and architectural aspects of his restaurants, and for Isola he began by commissioning plans from Iraqi buzz architect Zaha Hadid before moving on to Australian designer Andrew Martin. The restaurant has two parts. Upstairs is Isola proper, and downstairs is the more rough-and-tumble Osteria d'Isola, which will be a shade or two cheaper. And why the name? "Because one of my favourite places is Isola by Lake Como," explains Peyton. Isola is, as Martin puts it, "a big restaurant but not a `big' restaurant". It is not intended to be brash and mega. "I'm trying to make it mish-mashy rather than overblown," says Peyton. And unlike many restaurants, including the Conran ones, it is not heavily branded. Peyton's place is not intended to be a suits' playground. He actively wants to discourage what he tags the "Harvey Nicks estate agents" by leading with wine, rather than beer or coloured cocktails.

What he is aiming for is a "physical landmark". This has not endeared him to the residents of the 94 mansion flats above Isola who have stretched his budget by demanding extra sound-proofing. But such a vision has to be expensive - the restaurant is costing about pounds 3.8m (pounds 1m more than the original budget). Obviously, Peyton hopes his investment will be rewarded. But he wants to avoid "turning" (the practice of encouraging people to leave so as to fit in more sittings) and "snotty service", while maintaining a grandeur. "This is our flagship and we're spending more than ever before," says Peyton, who thinks that it will stand up to world scrutiny. "You'll feel that this is a place where you can take New Yorkers." To analyse what enables a restaurant to become more than the sum of its parts, one might employ the old chef's invocation - to let the ingredients speak for themselves.

Isola, 145 Knightsbridge, London SW1, 0171-838 1044. Osteria d'Isola can be contacted on 0171-838 1055

Fresh buffalo mozzarella with pickled vegetables

At Isola, the accent is on provenance. "My whole philosophy for Isola has been to get Italian produce," says head chef Bruno Loubet, who has insisted on "the best ingredients, cooked with respect." Items such as the buffalo mozzarella (above) therefore come from Italy. Other ingredients have been sourced from France and, when possible, the UK. The grand design

Peyton is an enthusiastic patron of the visual arts, and has installed a wall full of bizarre figures by the American artist John Currin for Mash in London, which fitted in with the skewed space-age aesthetic of the place. The artwork in Isola is by Richard Prince - another US artist - who is known for his Wild West imagery. "He designed it specially for us," says Peyton. "It depicts a horse on hind legs with a cowboy in full regalia sort of calming it down. He thinks it's one of his best." It hangs alone on one of Isola's walls. "There's only one piece because it costs so much money," he winces. Peyton has garnered a reputation for commissioning artists, and for using their work not just as add-ons but as part of the very fabric of his restaurants. In earlier ventures he used Young British Artists, from Damien Hirst wine labels in The Atlantic Bar & Grill to an Angela Bulloch installation at Coast. Martin (pictured left with Peyton, far left), being more spatially purist, isn't so sure about the Prince piece. "It covers an enormous part of one of the walls. I don't know - if I'd had my way I wouldn't have done it. I don't think it needs it."

Murano chandeliers

The Italian-centred concept extends to the lighting, which was commissioned at some expense from the glass houses of Murano, near Venice. Downstairs in the Osteria are green table lights while upstairs, in the grander Isola, tables have twinkling green night-lights which are complemented by six large chandeliers above. "We went to Murano because they can get the colour right and the shape right," says Martin. "They are brilliant - you can just draw a circle, send it off and it comes back much better than your drawing." There is extra lighting that is mostly concealed behind walls and chairs, and some light sources are hidden under banquettes. The two parts of the restaurant are linked at the front by the two-storey glass facade, providing an atmospheric unity between the two floors of Isola and Osteria.

Citrus fruits in lemon-liqueur jelly with avocado ice cream

Chef Loubet is taking an innovative approach to desserts, rolling out such beguiling recipes as this citrus fruit jelly. "It may not be too authentic, but I like it," he says. "The avocado has a flavour that goes well with citrus fruit."

In the kitchen

Peyton has 700 employees - 40 of whom work in these two restaurants - but he's found that there has been a shortage of suitable staff during the recent hot economy. Bruno Loubet has cannily carried good people along with him; one Filipino and one Hong Kong-Chinese chef have been brought back from his recent sojourn in the Far East, and he has high hopes for them. He says that these days a chef has to be an all-rounder, unlike the times when there was a specialist for almost every task. "Now you do a bit of everything," he says, "though you do still need specialists in pastry, and obviously if one guy is good on sauce you put him on that." Also crucial - particularly in these days of instant fame - is the right attitude. "Sometimes people can cook really well but they have such a bad attitude that if you take them on board it's detrimental. They'll moan so much that sometimes it is better to have people who are not so good but with a right attitude." One problem is that young chefs expect instant success. "They are driven by profit and fame, and don't want to spend 70 hours a week in the kitchen, which is quite normal in catering," he says. "What I try to do is tell them that this may be the situation at the moment but it may change, and if you are 25 years old you should expect three to five years of hard work before getting to a certain level."

The wine list

"The wine list is the mother ship," says Peyton, now a connoisseur of Italian wines. It is entirely Italian apart from the Champagnes, which Peyton concedes are a "must-have" in a power-dining scenario, although he will have Italian sparklers such as Proseccos. "It is partly a process of education," says Peyton. "British people associate Italian wine with terrible Pinot Grigio." He thinks that our lack of knowledge of Italian wines could be due to the Italians' attitude: "They like to keep the best stuff to themselves." The wine list is divided by region and variety. "The idea is to get people to drink wine by the glass, including Brunello at pounds 40 to pounds 50 a glass," says Peyton. "There are 64 wines by the glass alone." There is also a "taster" list enabling diners to sample five different wines in smaller glasses. The cheapest is the Chardonnay taster at pounds 16.70. Isola's wine cellars are situated behind the bar in the Osteria, which is underneath the road and lit so as to become a visual feature.

Poached hake with squid-ink stew

The dishes at Isola are a mix of classics, Italian regional dishes and some Loubet originals or, as he puts it, "interpretations" such as this: poached hake with squid-ink stew. He would like to achieve an Isola signature dish, but there are certain things he doesn't want to alter. "Some we will keep 100 per cent classical, like carpaccio," he says. There is no pizza on the menu, and Peyton is hoping that people will order pasta in the Italian way, as a starter rather than a main course. That a Frenchman like Loubet is head chef at an Italian restaurant might seem inconsistent, but Peyton says that he couldn't find the right Italian for the job. In any case, Loubet sees the two kitchens as springing from the same well. "At the end of the day, French food comes from Italian," he says. "It may be handled slightly differently but it is often the same principle."

Open kitchen

"If I were a foodie, I'd love to sit here and watch through this window," says Peyton, who liked the idea of providing a view of the kitchen for the diners. This is a hangover from the Zaha Hadid plans, the space is finished with red tiling and big enough for 40 staff to work in. It will be quite an experience for Loubet who, before becoming involved with Peyton and Isola, had set his heart on running a small, simple, neighbourhood restaurant. But having worked in several restaurants including the large L'Odeon on London's Regent Street, he feels up to the challenge, and is keen to raise the British culinary stakes yet further: "There are still not that many great restaurants in London - I think there is room at the top." The chef goes on to say, however, that the British are now sophisticated consumers. "In London there is more general knowledge of food than in many places in France," says Loubet. "They have a wider, more travelled perspective, and are more demanding."

Concrete tables and leather sofas

One of the architectural endeavours of Isola has been to allow space to flow: between the two restaurants, beneath floating floors and under the tables. It is a facet of the restaurant that invokes a touch of drama, and customers may experience a frisson as they realise the 10 cantilevered tables have no supporting legs. "There is a lot of fixed seating, which is quite American," says Martin, "but we also have a fair amount of flexible seating." The seating upstairs is red leather, made by an Italian company which also makes car seats for Ferrari. Downstairs in the Osteria, there are off-white white leather seats, which are, as Peyton puts it, "a compromise between a chair and a sofa". Again made in Italy, they are part of Peyton's effort to get Britons to eat en masse, like Italians, with shared plates and shared seats. Simon Hopkinson returns next week for a special issue on food and drink