La Petite Maison 54 Brook's Mews,London W1

Dateline: July 2007. Location: a Mayfair cul-de-sac so discreet that our driver has to be blindfolded before taking us there. Our mission: to infiltrate La Petite Maison, the latest celebrity restaurant, modelled on a famous Nice institution where the élite meet to eat.

Our cab pulls up before an undistinguished frontage. "This can't be it! It looks awful," protests Helen Fielding, one of my guests, who has been promised something glamorous. I whip out my press release. "No, this is definitely the right place..." At which point the man sitting outside interjects, "The entrance is around the corner." We thank the owner, for it is he, and slink in.

Gah! as Bridget Jones would say. For a restaurant critic and someone who has written a spy novel, it shouldn't have been that difficult. Still, we needn't have worried too much about blowing our cover. The scurrying staff were much too focused on their heartland clientele, a spread of grand old Mayfair types, big-haired blondes, trustfund twentysomethings and Max Clifford, to make a fuss over the likes of us.

Not since I went to Cipriani, another Mayfair spin-off of a much-loved European original, have I looked around a restaurant with the more certain knowledge that I would not be coming back. Not because of the food, which was good rising to excellent. But because the bland, moneyed dining room offers all the atmosphere of a polo tournament's corporate hospitality suite, with the same certainty that you're not going to bump into anyone you know.

Modelled on the Nice original (apparently Elton John's favourite restaurant), it's part posh-hotel dining room, complete with bad art and towering arrangements of lilies, part faux-rustic bistro, with each table ludicrously adorned with a lemon and two vine tomatoes. The overall effect is about as Mediterranean as Alan Titchmarsh.

The menu recreates the original's authentic Provençal cuisine, a fusion of southern-French and Ligurian influences designed to be eaten on a vine-shaded terrace rather than a landlocked London mews. Like the décor, it's a mix of the humble and the luxe; hors d'oeuvres range from a £4.50 green lentil salad to a crab and lobster salad at £16.50, while mains rise from gnocchi to a whole roast black-leg chicken stuffed with foie gras, at £35 to share. In fact everything on the menu is served to share, something more commonly found in Oriental restaurants (coincidentally, La Petite Maison's owner is also the backer of Zuma and Roka).

A salad of broad beans with shaved pecorino used the youngest shelled beans, as vividly green as the edamame served at the head chef's previous HQ, Roka, and similarly dull. Punchier was an assembly of super-fine haricot verts tossed with tiny cubes of foie gras and diced tomatoes. The best thing about the beignet of courgette flower, mysteriously accessorised with a single deep-fried anchovy and a solitary sage leaf, was the incredible tomato sauce that accompanied it. Salade Niçoise, no doubt impeccably traditional, was not exactly a revelation. "It's basically everything we've already had, thrown together in a pot," as my other guest Daniel observed.

In keeping with the faux-rustic theme, the aproned staff plonk chunks of springy pain de campagne straight down on the table, as if to say, "Oh, we don't stand on ceremony here. This is just a simple place serving simple Provençal food." As Lulu and Nasty Nigel from Pop Idol, sitting over there, will no doubt confirm...

Unfortunately, given that we'd already decided to hate the place, our main courses were superb. Sea bream came baked in a salt crust, adding a smoky richness to the fish that worked beautifully with the accompanying girolles. Grilled tournedos was a perfect specimen, if a slightly skimpy cut, to share between three of us. Helen was particularly uncomfortable with the sharing, which entailed eating fish and meat from the same plate, something that reminded her of a wedding buffet. But then, looking at the bronzed whippersnappers busy spending their parents' money all around us, she decided it might be a deliberate policy. "They've all grown up in hotels. They probably don't feel comfortable unless they have several different sorts of luxury foods on their plates."

The sharing system collapsed at the pudding stage, with Helen making short work of the chocolate fondant while Daniel and I were still virtuously working our way through the melon soup. Both were good, as were the £30 Fleurie and £23 Macon Pierreclos we tried from a wine list that offers a dozen different rosés.

Rosé may be charming when you drink it in Provence, but get it home and it's always disappointing. Similarly, something has been lost in translation in this attempt to import Mediterranean magic to Mayfair. Far from having any authentically French atmosphere, La Petite Maison occupies international waters. It's the latest addition to the theme park of brand extensions springing up in London to cater for the influx of wealth washing through the city. And though, like Cipriani, it will probably win a fanbase among the inhabitants of Richland, it seemed plain weird to us.

Our reaction hasn't been shared by other early visitors, who have given La Petite Maison rave reviews. Obviously those responsible aren't as crippled by class hatred and financial resentment as I am. And in fairness, the place isn't that expensive by Mayfair standards; we paid around £70 a head including service and wine. As we left, I was handed a Magic Marker and invited to add a message to the graffiti scribbled by well-wishing patrons on the maître d's station. I could feel Nasty Nigel's eyes on me as I crouched down to add my hypocritical "Wow!" to the good luck messages. Well what was I meant to write? "Killjoy was here"?

La Petite Maison 54 Brook's Mews,London W1 (020-7495 4774)

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Around £70 each including service and wine

Side orders: A taste of the Med

Le Suquet

This chic French restaurant in the heart of Brompton Cross transports the Sloane Ranger crowd to the sunny Côte d'Azur. The prices are high and the knick-knacks are kitsch and nautical – but the fish stew and sparkling seafood platters are sublime.

104 Draycott Avenue, London SW3 (020-7581 1785)

The Olive Tree

Located in the historic centre of York and enjoying a view of Clifford's Tower, this friendly, family-run restaurant sources the produce for its classic Mediterranean dishes from a range of local manufacturers: try the tuna steak with niçoise salad and quails' eggs, and seafood risotto with saffron cream.

10 Tower Street, York (01904 624433)

Le Garrigue

This Edinburgh restaurant specialises in classic cuisine from the Languedoc. At £21.50 for two courses, the dishes include a Mediterranean fish soup and a Roquefort soufflé with artichoke and ratatouille. The excellent wine list is also sourced from the region.

31 Jeffrey Street, Edinburgh (0131-557 3032)

The Summer House

Part of the Summer House Hotel, this acclaimed Penzance restaurant has a daily Mediterranean set menu which depends on what comes in on the boat that morning. If the weather is good enough, eat in the walled garden, close your eyes and imagine you're in Cannes.

Cornwall Terrace, Penzance (01736 363744)