Roka, London W1

Everything on the plate in a Japanese restaurant is a metaphor. You know the white radish on a sashimi arrangement, the way it sticks up in the air?

Everything on the plate in a Japanese restaurant is a metaphor. You know the white radish on a sashimi arrangement, the way it sticks up in the air? That's because it's trying to attain a state of perfection. And what do I do? I come along and eat it, and offend everyone in the place with my philistinism - you know, like, eating the food. That is why I always gave Japanese restaurants a wide berth.

Zuma in Knightsbridge was different. It was an informal and achingly contemporary place to eat Japanese food. But so expensive. There is an old Japanese proverb - "Poverty is no sin, but it is terribly inconvenient." Nowhere is it more inconvenient. I had high hopes that Roka, which is run by Rainer Becker, the restaurateur who owns Zuma, might be cheaper. A man can hope.

The name Roka is derived from the Japanese words "robata", the flaming grill which forms the central feature of the dining area, and "ka", or fire. So I decided not to wear a cardigan. As I walked to our table, I noticed two men working on the broken air-conditioning. A cardie in Roka would definitely have stopped me attaining my state of perfection.

Everything about the place, with its golden honeycomb walls, was warm and inviting. Because they are grilling over charcoal (so much better than gas), a six-foot flame would rise from the robata every so often. But the cooks, in their understated black linen, didn't turn it into theatre. They were concentrating too intently on preparing the food.

The menu was difficult to understand. It was in English, and the descriptions of the food were more than adequate, but the categories were confusing. Maybe most people know about sushi and sashimi. But chu-maki? Or robata yasai? And if I have a robata sakana, will I be too full for a kushiage? It assumes far too much knowledge, and far too much patience from a busy team of waiters with 80 covers to serve.

We began with steamed edamame (£3), fresher than I'd eaten before, with sea salt turning their blandness into something rather delicious. Japanese cooking uses almost no spices. Instead, the emphasis is on pure, clean flavours. For the edamame, it worked perfectly.

The same could be said of the five-piece sashimi selection (£21) - the slabs of fish melted on to the tongue, and left a delicate taste of the sea. There wasn't a big choice of sushi, but then, these days, sushi is available at Tesco. The egg roll was topped with paper-thin flakes of bonito, a dark, oily fish that the Japanese smoke and dry and use as a seasoning. It's everywhere, and is a vital ingredient in dashi, the base stock for most Japanese soups and broths. The heat from my egg roll caused the bonito flakes to flip and flap - like a fortune-telling fish. They curled up at both ends, which means I am jealous.

In fact I was jealous - I should have ordered my own sea bream fillet (£10.20). The tiny mouthful I did have (when my friend was in the gents) was exquisitely wet and fresh, luxuriating in a sweet miso sauce. The dish was the Roka equivalent to Nobu's signature dish of black cod. And the presentation was every bit as impeccable - a thing of beauty is a joy for seven or eight minutes if you don't stop to talk.

The yaki asparagus (£4.60) sounded nicer with the waiter's Japanese accent, but I couldn't bring myself to order it. Instead I went for kani no kama meshi (£12.90) - a Japanese risotto with king crab and wasabi tobiko. Even though it arrived at the table with ceremony, the lemon was overpowering and tasted artificial.

The lamb cutlets with Korean spices (£12.60) sounded a bit unlikely. What are Korean spices? I'm guessing, but red peppers and garlic? Like all grilled Korean entrées, I imagine it was meant to be eaten with side dishes such as kimchi, marinated root vegetables, bean sprouts in a sweet-sour dressing and shredded radish. But the waiter didn't point that out.

There's an extraordinary selection of Japanese comfort food, including onion rings in breadcrumbs (£4.30, with a barbecue sauce) and garlic mushrooms (£4.30). All of a sudden we were at a Harvester in Tokyo. But Roka is cheaper than Zuma, and the eccentricities of the menu will soon be ironed out. Even if it doesn't do a surf'n'turf, Roka is worth a punt. E

Roka, 37 Charlotte Street, London W1, 020-7580 6464

SECOND HELPINGS: TURNING JAPANESE

By Christian Broughton

Chino Latino

Miso and mojitos mix at this Latin bar/Asian fusion restaurant. Shinji Nakamura (ex-Tsunami, ex-Nobu and still doing black cod) makes his food heard above the DJs. Nottingham loved it; now it's up North.

Boar Lane, Leeds (0113 380 4080)

Izakaya

Wear your best socks: you'll be de-shoed if you take one of the traditional low-slung tables. Otherwise, eat your sashimi, noodle soups, tofu, etc, at a regular table with an uncommonly good view of the bay.

Mermaid Quay, Cardiff Bay (029 2049 2939)

Koo

The Merchant House and Hibiscus win the stars here, but Koo's set meals have long been filling stomachs without emptying wallets. It's just gone à la carte, but value and favourites (such as salmon in miso) won't be leaving.

17 Old Street, Ludlow (01584 878462)

Oko

In the increasingly hip Merchant City, in a stunning Victorian red-sandstone conversion, Jim Kerr's conveyor-belt bar offers sushi and loud music to diners on tall, heavy, shared benches.

The Todd Building, Ingram St, Glasgow (0141 572 1500)