Sushi had a dubious reputation among conservative British diners even before Alexander Litvinenko's murder made it sound as appetising as root canal work. Served a plate of raw tuna, many timid diners still wonder if maybe the delinquent chef forgot to turn the grill on.

But sushi has now become fashionable enough in Britain to be sold in supermarkets, even if Japanese would turn queasy at some of the innovations introduced - tuna mayonnaise and sweetcorn sushi, for instance - to enable less adventurous diners to tuck into the trend.

That's if you can still call some supermarket sushi sushi. It's not that you can't get so-so sushi in Japan. It's just that over there you'd have to search very hard, or pay very little, to find sushi made of hard, machine-moulded Lego bricks of frigid rice dabbed with a green tracer of wasabi horseradish (too small a smear to prick your palate, but just enough to suggest your sushi may have an infection), topped by a flap of fish that's so unattached to its base that you wonder if it's recoiling in embarrassment at being part of the enterprise.

It takes seven years to train as a sushi chef in Japan, much of it just learning how to sharpen a knife and studying slicing angles. Some very fine sushi restaurants in Tokyo are no bigger than a bathroom, brightly lit and Formica-furnished, where a chef slices fish with a surgeon's precision (two slivers from the same tuna can be a few inches apart in distance, but hundreds of yen apart in price), like the culinary master his drooling customers take him for.

And here? The shortage of native Japanese expertise in Britain results in many Japanese restaurants being staffed by vaguely Oriental-looking men and women in the hope of conveying the sprit, if not the letter, of sushi law. Not that this stops them charging Tokyo prices.

So where to eat? Nobu and Zuma are dandy; if you can get a table, and an overdraft. Stick to modest non-expense-account places frequented by Japanese expats in London, such as Inaho in Bayswater or Sushi-Hiro in Ealing, and your stomach and wallet should both be happy.

Or, do what I do: buy a sharp knife, locate a reliable fishmonger and roll your own.

The risk in a “sushi police” is that while seeking to tighten standards, they'll further swell prices in those restaurants they bless.

That would really be a raw deal, wouldn't it?

How the British brands compare

YO! Sushi (nationwide)

Rice currently grown in California
Soy sauce made by Yamasa, a Japanese brand
Miso paste sourced from Japan Approximately 95 per cent of their ingredients are Japanese in origin.
Meat, vegetables and fish are sourced locally. 95 per cent of their dishes are described as traditional ‘japanese inspired’ dishes
Average cost of a meal for one £20

Pret a Manger (nationwide)

Their Sushi Deluxe is made in Britain Japanese chefs
Rice koshi rice and Low Amylose rice, both grown in the US
Soy sauce Sourced from Japan along with konbu powder, vinegar, wasabi, mirin and sake
Some fish from Japan but others, including tuna and salmon, sourced more sustainably. Only use raw fish
Cost deluxe sushi box for one £4.95

Umu (London)

Rice grown in Japan
Soy sauce Tezukuri-Shoyu, Ginjyo-Shoyu, and Higashimaru Light Soy Sauce, all Japanese
Fish Kanpachi amberjack and striped amberjack come directly from Japan, as well as some shellfish, depending on the season
Cost set-menu lunch for one: starting from £21

Source: london-eating.co.uk ; YO!Sushi; Pret a Manger; Umu

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