It has inspired poetry and ignited trade wars. First it was used for medicinal purposes. Later, it became the world's most popular beverage, and even a ritual in Japanese marriages. Of the 2 varieties, black and green, the former represents 95 per cent of the world's production. The Irish are its biggest consumers, guzzling up to 8 cups a day per person.

Antony Wild's wonderfully illustrated The East India Company Book on Tea says that Jinuoshan's present-day Pu'er tea is a flavoured mix of Assam (black) and Chinese (green) teas, while the Oolong teas, grown mainly in Taiwan, are semi-fermented. Lapsang Souchong from south China has a thick dark liquor and a pronounced smoky flavour. Gunpowder, from North China, is a green tea whose leaves are rolled into little tight balls resembling cartridge shots.

Japan produces fine green teas, including Sencha, a steamed tea which is grown from unshaded bushes. Its astringency and high ascorbic content makes Sencha repulsive to the Western palate. Matsucha, the variety used for tea ceremonies, come from shaded bushes and the dried leaves are stone-milled to produce a fine fluffy powder.

The world's most expensive tea, however, is a Makaibari Flowery Tippy Golden Orange Pekoe, from Darjeeling, bought in 1992 for $360 per kilogram.