How Britons turn their backs on a waterworld of Christmas feasts

Here is an unusual thought for Christmas: fish. If there is one foodstuff most people in Britain do not have their minds on today, as we stock up for our great annual feast, it is the one with fins on.

We think blowout and we think turkey; at a pinch, goose. But in planning a protein party, so to speak, we never think carp and pike, as they do in Eastern Europe, or tilapia, as they do in Africa, or snapper, as they do in Asia. The idea of feasting and fish seems to be entirely foreign to us; but for much of the rest of the world, it's entirely natural.

Billingsgate, the historic fish market in east London, is packed with British fish buyers; at one stage last weekend you could not get your car in the car park. The point is that the weekend before Christmas is the one occasion in the year when this is so. People pile into the market to buy their holiday smoked salmon and prawns, with perhaps a few Yuletide lobsters and Dover soles on the side.

The rest of the year, the non-trade buyers at Billingsgate, the individuals who point and say "I'll have that one", are overwhelmingly from London's burgeoning ethnic communities: Chinese, Japanese, Filipino, Indian, West Indian, West African and East African. They are people brought up in a fish culture, who love and value fish as a protein source, who know how to prepare it and to cook it, who, as Chris Leftwich would say pointedly, are not afraid of it, as Britons seem to be.

Mr Leftwich is the Chief Inspector of the Fishmongers' Company, the ancient livery company of the City of London, which still retains the rights it has had since the Middle Ages to inspect all fish on sale in City markets and "gauge whether [it] be fit for man's body".

But the men from the Fishmongers' Company at Billingsgate are not just food safety watchdogs; they are also enthusiastic promoters of fish in a land where it does not seem to get its due.

Mr Leftwich said an average of two-and-a-half kilos of fish per person is consumed per year in Britain. In Spain, the figure is 40 kilos; in Japan, 65.

"A normal British family doesn't eat fish, doesn't understand it and is frightened of it," he said, looking around at some large denizens of the deep on the market slabs, which admittedly might put the wind up some people of a nervous disposition.

"Whole generations have not got a clue what decent fish looks like. There are people here every day from the ethnic communities buying fish that British people would not know what to do with."

To help change this situation, the Fishmongers' Company has set up a seafood school in Billingsgate, which gives courses in fish cooking and, perhaps more importantly, fish preparation, to everyone from schoolchildren to the fish counter staff of leading supermarkets, such as Waitrose.

Its reputation is slowly growing, though it is still not as well known as the company would like it to be. It is open to the public, and a popular, if expensive, course is knife skills, which is £125 for a day. "But you fillet an awful lot of expensive fish, and you can take it all away with you," Mr Leftwich said. "Knife skills are important and they're dying out."

He and his two inspector colleagues, Barry O'Toole and Robert Embery, are the quality control officers at Billingsgate; vital with a foodstuff which goes off quicker than any other, in a market that turns over 25,000 tons of fish a year.

They have powers of prosecution under the Food Safety Act for Tower Hamlets, the borough which contains the market (it is now at Canary Wharf), and for the Environment Department as Sea Fisheries officers, checking for under-sized specimens.

But prosecutions are the exception in a place where so much is perishable. "We usually give the merchant the option of surrendering unfit fish to us," Mr Leftwich said.

It is fascinating to watch him checking - especially on a Tuesday, when new deliveries arrive - so last week's not-so-fresh stock is most visible. He picks up a whiting: "The eyes have started to sink, see, and are going a little bit cloudy; the gills are browning up a bit. The merchant needs to get rid of these."

It is fascinating, indeed, just to walk around the bustling market with Mr Leftwich to enjoy his piscine expertise.

Here, he points out, are king scallops and queen scallops, the former with one flat shell and one round shell, and the latter smaller, with two concave shells. Here are dredged scallops, and bigger dive scallops, hand-caught by divers and on sale for £1.50 each.

Here are kippers, which are "cold-smoked" so you still need to cook them, and Arbroath smokies, which are "hot-smoked" so they are ready to eat. Here is whitebait, young sprats and young herring mixed together; tell them apart by running your fingers down the ridge of their bellies: those of the sprats are spiked; those of the herrings are smooth.

Here are British lobsters which must measure at least 87mm from the back of the eye to the end of the carapace, or hard shell. "We used to measure the whole animal, which had to be nine inches to the tip of the tail, but if fishermen caught an under-sized one, they would sometimes stretch its tail to make it pass," he said, grinning. "You can't stretch the carapace."

Here are farmed salmon and wild salmon. The idea that you can tell them apart when cooked, Mr Leftwich insists robustly, is a myth.

Here are great flatfish - like halibut and turbot - giant seabass and cod, tuna loins, stalls full of cephalopods (octopus, cuttlefish and squid). And here, most noticeably, are the exotics, the warm-water fish now regularly flown in to supply the taste of London's ethnic groups: barracuda from Somalia;crawler from Argentina; pomfret from India; parrot fish from Indonesia and snappers from all around the globe.

A Chinese man next to me is buying two enormous, whole, bright red fish, which turn out to be bourgeois snappers from the Indian Ocean. He hands over £50 for the two and said his name is Danny Yip. He owns a Chinese restaurant in Brixton, south London, and the fish are for a private party. They are going to be steamed. It seems to him the most natural thing in the world. Chris Leftwich said: "People from Asia and Africa are market-oriented. They enjoy coming here. They think they're getting a bargain. They eat huge volumes of fish.

"And we're an island, we're surrounded by water and we eat meat. Remarkable, really, isn't it?"