Restaurants: Sake No Hana, 23 St James's Street, London SW1

"So, how did you hear about us?" asks the tall, young man leading me up the long, narrow escalator to the first-floor dining-room. Is he kidding? I have been waiting for Alan Yau's latest venture for what seems like a year. Having given us noodles for the people at Wagamama and Busaba Eathai, and Cantonese for the cocktail set at Hakkasan and Yauatcha, this wildly inventive yet quietly behind-the-scenes restaurateur has now turned his hand to upmarket Japanese. I would have thought we had had our fill of those, but it appears London has not yet run out of very rich, skinny people. The question is, does Sake No Hana cut it for the rest of us?

While Yau might not own it the Aeroflot heir Evgeny Lebedev does the restaurant is very much his baby. The Japanese architect Kengo Kuma has turned the awkward space of a modernist landmark building into a shimmering urban forest of blond wood and bamboo, a Shinto shrine for the secular. A raised platform allows for traditional low-level seating, creating an air of temple-like elegance that is almost spoilt by the arrival of people.

The menu takes a bit of deciphering. It's not the kaiseki banquet cuisine of Mayfair's Umu, nor the grill-driven izakaya tavern style of Zuma, nor the mod-Jap of Nobu. Instead, it is a mix of Japanese classics: home-style braises, raw fish and noodles, grouped under cooking methods such as yakimono (grilled), agemono (deep-fried), mushimono (steamed), takiawase (simmered), sushi, and sashimi, here called tsukuri, a colloquial term used in Osaka and Kyoto.

Status foods abound, from Wagyu beef in miso for 55 to white truffle rice for 70, and it is difficult to know whether you are ordering something small or large.

A tiny salad of king crab and marinated cucumber filaments (8) is fresh and pretty. Tempura prawns (2.50 a piece) are limp and bland. Nasu iridashi (3.50) of warm marinated baby aubergine, flavoured with sesame and topped with pencil shavings of dried bonito, has a Zen-like simplicity. A pot of glazed freshwater eel served on rice (13) has potential but the eel is soft and mushy.

Sushi features shimmeringly fresh fish and delicate handling; both maguro tuna and seabass nigiri (3 a piece) are as good as you will find at Zuma or Marylebone's Dinings.

No wine is offered at Sake No Hana, and the cheapest champagne by the glass is Krug for 30, so I am forced to take a sudden interest in sake. From the 50-strong list, the enthusiastic sommelier, Stuart Hudson, suggests 180ml carafes of creamy, nutty white ginjo from Nechi Otokoyama (15.50) and akai from Asamurasaki (14), a smoky, strident red-tinted sake made from red rice, which works well with a large witches' cauldron of aromatic, soy-simmered black-leg chicken (24). Its tender meat is taken from the bone at the table and folded through the sweet juices, carrots, soy beans and sugar snap peas. Flavours are gentle and subtle, yet deeply satisfying, but I would chew my arm off for a pinot noir.

Fellow diners are so sleek, glossy and black-clad, it is like being in the middle of a seal colony, as they throw back their heads to toss down morsels of gleaming fish. The beautifully dressed servers (another Yau signature) are knowledgeable and caring, although still struggling with the edicts of the kitchen. Ordering a coherent meal appears to be some sort of test one is simply expected to know how. And while I admire the purity of the sake-driven concept, I find it offensive to forbid wine and yet allow the odious Diet Coke.

Sake No Hana is undoubtedly a class act, impressively designed as a conduit for some very fine talents. It remains to be seen if it has what most of us want from a Japanese restaurant. But then, I'm not entirely convinced it is interested in most of us in the first place.

15/20

Scores: 1-9 stay home and cook, 10-11 needs help, 12 ok 13 pleasant enough, 14 good, 15 very good, 16 capable of greatness, 17 special, can't wait to go back, 18 highly honourable, 19 unique and memorable, 20 as good as it gets

Sake No Hana, 23 St James's Street, London SW1, tel: 020 7925 8988. Lunch and dinner, 140 for two, including sake and service

Second helpings: More Japanese joys

Nambu-tei

12 Thames Street, Windsor, tel: 01753 842 186

This smart, modern-Japanese diner serves up all the usual favourites, within a chopstick's throw of Windsor Castle.

Yukisan

51 Notte Street, Plymouth, Devon, tel: 01752 250 240

Yukisan claims to be Devon's only Japanese restaurant. For the full authentic experience, ask for a seat upstairs in the Japanese room.

Dinings

22 Harcourt Street, London W1, tel: 020 7723 0666

There is barely room to swing a catfish in this tiny Marylebone restaurant, but chef Tomanari Chiba and his team turn out exemplary sushi and inventive "tapas"- sized dishes such as crab tartare tacos.