Fishy facts

* The longest sushi conveyor belt in Britain is at Yo! Sushi in Soho, London, which measures 60 metres; the longest in the world is at Sakae Sushi in Singapore, where diners select dishes from a 129m-long belt.

* Sushi made with fatty tuna, called otoro, is the most highly-prized in Japan. It is served at room temperature, so that diners may appreciate its 'melting' texture.

* True sushi fans know to dip the topping, rather than the rice, into the soy sauce, using your fingers, not chopsticks.

* There are 277 Japanese restaurants in the capital, according to Visit London. At Nobu in Mayfair, a single piece of otoro sashimi costs £6; at Yo! Sushi, £3.50 buys you 5 slices of tuna sashimi.

* Most seafood is low in fat; and any fat is present is generally rich in omega-3. Since most sushi is raw (a notable exception being eel nigiri), little fat is used in its preparation.

* Those on a low-GI diet may note that fish, tofu, seafood, egg and many other sushi staples contain high levels of protein. Order sashimi – and hold the rice.

* There are a mere 37 calories in a piece of regular tuna nigiri; eel sushi contains 65 calories.

* Wasabi, the fiery paste made from the underground root of the wasabi plant, may feel like it blasts your sinuses, but it is not, California doctors have concluded, actually an effective decongestant.

* Essential vitamins and minerals are found in the vegetables used for sushi; for example, nori contains vitamins A, B1, B2, B6, Niacin and C.

* Traditionally, egg omelette sushi is eaten at the end to calm the palette and settle the stomach.