Sumosan, London

Sumosan might well be the place to be seen, and its business-class menu does not disappoint, but, as Tracey MacLeod discovers, it's no Nobu

Restaurants that thrive on the patronage of the fashionable are playing a risky game. The in-crowd rapidly moves on and the sizzle of excitement surrounding the place evaporates, leaving the rest of us looking around in vain to see if there's anyone we recognise.

Restaurants that thrive on the patronage of the fashionable are playing a risky game. The in-crowd rapidly moves on and the sizzle of excitement surrounding the place evaporates, leaving the rest of us looking around in vain to see if there's anyone we recognise.

Oliver Peyton's Coast, when it opened in Mayfair in 1996, was hugely fashionable, as well as huge, with its sci-fi Marc Newson interior and directional cooking from the likes of Stephen Terry. For the first few years it was packed, but maybe it was just too groovy for this resolutely stolid part of Mayfair, where Browns is the new black. Having briefly converted it into a branch of Mash, Peyton gave up on the site.

After a long refurbishment, which ran months over schedule, it has now re-opened as Sumosan, an expensively fashionable Japanese restaurant. It's the first UK venture of the Wolkow family, whose four Moscow restaurants (including the original Sumosan) are apparently a favourite with jet-setters and rich Russians, from Naomi Campbell to Mrs Putin.

In the transformation from Coast to Sumosan, a pupa has emerged from a butterfly. Newson's lime-green walls have been replaced by a neutral beige and taupe un-colour scheme (actually created by a company called Neutral Design). It's a backdrop to fabulousness; a stage-set in which gorgeously dressed people can look their best, without being upstaged by the furniture. When we turned up for dinner on the Friday of opening week, at the unfashionably early time of 8pm, they hadn't arrived yet; we were Sumosan's only customers, apart from one other cowed-looking couple. The staff/client ratio was reminiscent of Camp X-Ray; a mass bowing of sushi chefs broke out as we passed their counter, and a phalanx of waiters rushed us with menus when we sat down. The theme from A Man and a Woman played in the background, neatly summarising the clientele while keeping them entertained.

Sumosan is already attracting comparisons with Nobu, in that it serves modishly adapted Japanese food in designer surroundings. Interlopers like Peking duck and goose liver lurk among the traditional varieties of sushi and sashimi, and the inclusion of black cod with miso, Nobu's signature dish, seems to be throwing down a gauntlet. The rest of the list, however, doesn't match Nobu's eclecticism. Still, I wanted to sample some of the more outré offerings, and ordered the itadakimase tasting menu, beguiled by its promise of special dishes made "with the finest ingredients available from the market each day". Our waitress duly undertook to ask the chef for his most unusual creations.

Before they started to emerge, she offered edamame – fresh soy beans, steamed in their pods and sprinkled with rock salt; we could almost feel them doing us good. Our banquet proper started with the kind of salad they do so well in California, teaming perfectly ripe avocado with fat prawns marinated in ginger, and topped with crab meat. It was good, but the inclusion of raw red onion so early in the meal struck me as misguided – its lingering taste skewed our palates, and our appreciation of the sushi and sashimi which followed suffered as a result, though we could tell the sushi was notably fresh. The sashimi selection seemed unadventurous considering the chef's promise to have combed the markets on our behalf. Maybe he decided to go to Portobello Road that morning instead of Billingsgate.

The story was the same as our meal progressed; the food was mainly fine, in an international business-class kind of way, but nothing delivered the kind of fireworks we were expecting, and nothing was particularly unusual. The highlight was probably a selection of three raw fish tartares (salmon, tuna belly and yellowtail), served over ice and dressed in an iced soy and wasabi sauce. A heap of tiny rock shrimp were fried in a tempura batter and paired with a spicy dipping sauce; so abundant was the portion that the crisp morsels had turned soggy by the end, like the contents of a Glaswegian's chip bag. A similar fate awaited the vegetable and prawn tempura in an udon soup.

Curious to see how it matched up to the Nobu version, I had made a special request that the centrepiece of our banquet should be the black cod with miso. But it's a very rich dish, and by this stage we were feeling like contestants in a Japanese endurance game-show, about to face the final, impossible challenge. Luckily there was a lengthy hiatus before it arrived. We were able to sample enough to note that it had the authentic sticky sweetness and fell apart in big, soft flakes, but it was also fairly bony, something I've never encountered at Nobu.

Our banquet ended on a bathetic note with sliced fresh mango and banana served with vanilla ice-cream. A study of the menu revealed that all the dishes on our tasting menu, supposedly created by Sumosan's chef from the finest ingredients from that day's market, also appear on the regular list, mostly at the more expensive end. In a serious restaurant, it just isn't good enough to put this kind of promise on a menu if it isn't true. It made me feel I'd been had, a feeling that wasn't helped by having to stump up an extra £2.75 for the soy bean appetiser, on top of £55 a head for the tasting menu.

By offering consistently dazzling food, Nobu has managed to buck the fate of other fashionable restaurants, and remains booked out for weeks ahead. A fair-sized crowd of diners and drinkers filled Sumosan by the time we left. I'll be curious to see if they're still there in a couple of years' time.

Sumosan, 26 Albemarle Street, London W1 (020-7495 5999)