Sushi bars are opening all over the place, in London at least, and now supermarkets are stocking up on sushi trays. Waitrose was first, and Tesco and Sainsbury's have started up in their more avant-garde stores.
This uniquely Japanese speciality is an unlikely candidate for national acclaim, for until recently sushi has been consumed only in London's Japanese restaurants. But experts now claim it perfectly fits the buoyant mood of the day.
"Sushi looks good, it's tasty, and above all it's perceived to be incredibly healthy," says Nellie Nichols, food development officer of Pret-a-Manger, the burgeoning sandwich chain with 50 branches. It introduced sushi boxes several years ago and has seen sales rising steadily ever since. It sells 2,200 boxes a week at pounds 2.70 and 3,700 de luxe boxes at pounds 4.95. The latter consist of two rice rolls stuffed with raw slices of blue- fin tuna, one with raw salmon, one with white fish, one with prawn, and three rice rolls wrapped in the Japanese seaweed sheet called nori, with accompanying soy sauce, a blob of green wasabi (Japanese horseradish), marinated ginger and a pair of chopsticks.
"People of all ages love it," says Ms Nichols. "They really like the look of it, it's so colourful and interesting. And, especially, there's the feeling it's really good for you."
It took off in London, and now it's beginning to catch on in such branches as Oxford, Cambridge and Birmingham, she says. And sushi bars are popping up all over London. Liverpool Street was the first railway station to boast its own sushi bar, and Harrods has been the first department store, its nine sushi staff hard-pressed to keep up with demand.
Anton Edelmann, the health-conscious chef des cuisines of the Savoy, was first to introduce sushi to the clientele of a top hotel. He says: "I visited Tokyo in 1986 and thought it was wonderful. All you need is some Japanese rice, Japanese vinegar, horse radish and some very fresh fish. It's very easy in its simplest form. I'm told the Japanese require a three- to 10-year apprenticeship to learn to make it. I can't think why."
He is not surprised that sushi is taking off. "Sophisticated eaters caught on very quickly. The broad masses haven't. But they will - it floats down."
Raw fish, he realises, isn't everyone's idea of fun, so he doesn't yet offer it on the hotel's daily menu. But it's an option for customers booking parties there.
"Sushi rolls are lovely," says Mr Edelmann. "I call them Perfect Morsels. They are food for the eye. They stir your senses, they are very sensual."
But sushi is not necessarily a cheap option. "The fish has to be very, very fresh, and tuna, sea bass and brill are expensive. On the other hand, a little fish goes an awfully long way."
If sushi does become widely popular, much of the credit will have to go to Werner Schulz, Waitrose's sushi buyer. He approaches his role with missionary zeal. He has introduced sushi to 14 stores and by the end of February it will be 18. Prices range from 99p to a family-sized pounds 14.99.
"Before it goes on sale, I visit the store with some packs the Friday before. The staff meet me with some trepidation. They have an idea what it is, rice and raw fish, and they frankly admit they don't like the idea. 'OK, I say, but what is smoked salmon but basically raw fish with the addition of 3 per cent salt? You eat that.' Gradually they try it, and they all like it. 'I'd buy that myself,' they say. This gives them the confidence to recommend it to customers. It's going great guns."
He did a Tasting Table in South Harrow. "I was really surprised to see middle-aged gents and elderly ladies tucking in. I believe the customer recognises quality. Freshness is essential. The sushi are actually made during the night, and go on sale in the morning."
But is the rest of Britain ready for raw tuna? Tesco and Sainsbury's have put Mr Ko's sushi on sale in a few key stores. Marks & Spencer has been watching too, but says it wouldn't be happy to put out a product that couldn't go into stores right across the country.
"It's a London fashion," says chef Mark Gregory, a New Zealander who worked in Japan and introduced sushi to his own country. "I don't mean it in a rude way, but it will be a long time before sushi goes north of the Watford Gap."
Mr Gregory serves it at Brocket Hall in Hertfordshire. "I do compromise," he confesses. "Most of my customers don't like the idea of raw fish, so I use smoked salmon or cooked crab or avocado in the rice. It's still a wonderful lunch snack."
The Michelin Guide and the Good Food Guide are not aware of any serious signs of a sushi surge outside London, although the odd sushi bar turns up in Manchester, Leeds, Edinburgh and Glasgow. "I'm surprised it hasn't happened before," says Jim Ainsworth, editor of the Good Food Guide. "Sushi is very attractive and it should be cheap. I foresee a snag, though: can we get our hands on enough spanking fresh fish?"
In Newcastle, chef Terence Laybourne, owner of the Michelin-starred 21 Queen Street, says he buys sushi at a little Japanese deli in Heaton Road. "I love it, but sushi hasn't made the headlines up here yet. Of all the new food fads, I don't think it's one that would ever work in the North- east. The flavours of Japanese food are too subtle for crude northern palates."
At the Roscoff in Belfast, where owner-chef and TV cook Paul Rankin occasionally makes some for parties, his assistant explained that he does them only for people he knows very well. "The idea of eating raw fish here in Ireland, you know ... they won't do it."
Japanese restaurants apart, sushi hasn't filtered through to other London restaurants.