The first sake was produced in 3rd Century Japan, and called "kuchikami no sake" or "chewing-in-the-mouth sake." Rice, chestnuts and millet would be chewed by the whole village and spat out into a tub to ferment. It was an important part of Shinto religious festivals - with sake being offered up after harvest, wedding and New Year's celebrations.

Often erroneously called "rice wine", sake being based on a cereal, is actually a beer, though its strength of 15% to 20% alcohol by volume makes it taste wine-like. Unlike wines sake doesn't age well - it should be drunk within 7 to 8 months.

As with all beers, the chief production challenge is how to convert its unfermentable starches into fermentable sugars. Barley is malted to render it fermentable; with sake, 'koji' is used.

Grains of special sake rice (Shinpaku-mai) with a high starch content in the core of each grain, are washed, soaked, steamed and cooled. Koji (Aspergillus oryzae), a fungus, is then sprinkled on. When left in a warm damp room for a few days, enzymes are produced which convert the rice starch to sugars. The final product created by adding water and yeast and leaving for 3-4 weeks.

In addition to the quality of rice, the climate and water in the production area are crucial factors. Water comprises as much as 80% of the final product hence Sake breweries in Japan are located near some of the best spring water in the world. Pure water leads to a sake full of rich flavour.

This is a description of the traditional method of sake production, but the Second World War created an inferior brewing technique. Rice shortages forced brewers to add pure alcohol and glucose to small quantities of rice mash, which increased the yield by as much as four times. This method now accounts for 95% of today's sake. This is why European and American people think sake should be drunk warm - but high quality sake is best consumed cold, or even on the rocks.

Sake is falling out of favour in Japan - it's association with the older generation means many young Japanese prefer drinking red wine to going to their local Izakaya (sake bar) nowadays - an effect of westernisation. It's high alcoholic strength counts against it too: "If drinking sake, too much drunk. Cannot play TV game," commented Mr Kohiyama of Takasago sake brewery.

A fifth primary taste, recently identified by researchers known as umami is found in sake. There were previously thought to be only four primary tastes, detected on different zones of the tongue: sweet, salt, sour and bitter. Umami is also found in soy sauce and miso, both of which are made using the same koji techniques.

Japan still has 1,800 sake breweries - most are micro-brewery sized and family-run; the sakes produced by all but a handful have never been exported. Throughout May, however, as part of the Japan 2001 celebrations, Selfridges will be selling 34 sake varieties from 18 different breweries up and down Japan.

Kanpai! (cheers!)