We eclectic imbibers are always looking for an excuse to dust off a bottle that has been neglected. So on Thursday I shall uncork the tequila and raise a glass to Cinco de Mayo, the most celebrated of Mexico's independence days. I may even prepare a chicken mole for dinner.

Tequila, and Mexican food, deserve more respect. The drink's image has suffered since a group called the Champs recorded the daft song 'Tequila'; the food merely suffers from a surfeit of pancakes. I have enjoyed both on their home ground.

The road north-west of Guadalajara, in the western state of Jalisco, climbs into a high desert of granular soil that looks like drinking chocolate. Soon it provides vistas of fields full of tall, spiny, turqoise plants, then the small town of Tequila, behind which rises a volcano of the same name.

The plants, though cactus-like, are a member of the lily family, and the local 'blue' variety is known as mescal, a type of agave. The hallucinogenic mescaline comes from the peyote cactus, but tequila and the primitive drink pulque both are derived from the agave.

At the roadside, I ignored the pecan and honey vendors in favour of a pulque-seller. He told me that the flower stalk of the agave was cut to provide the sap on which his pulque was based. The sap is passed through a bamboo tub into a gourd, then decanted into a wooden barrel to ferment spontaneously overnight.

The finished pulque is a milky greyish colour, and tastes lactic, sherberty and fruity. I also sampled a version laced with a chilli sauce and garnished with diced onions and a turnip-like vegetable called the jicama.

Though pulque was made before the conquest of Mexico, the Spanish introduced the art of distillation, and called their distilled product vino mescal. Elsewhere in Mexico, this spirit is known simply as mescal, and is often served from what looks like a petrol can.

The more elaborate bottled examples sometimes contain a 'worm' - a caterpillar-like bug that bores into the plant. The survival of its body, intact, in the bottle is said to be a sign of the spirit's high alcohol content, and the consumption of the worm an enhancement of manliness.

I steeled myself to consume one, but it tasted like nothing more challenging than a twist of paper, and had as much effect. The mescal itself has an earthy, charred- wood character. In Britain, look out for one called Bronco.

It is mescal made specifically from the 'blue' variety of agave in a denominated region of Jalisco province (and three bordering states) that is permitted to bear the appellation tequila.

In the wild, the plant grows to 15ft, and is cross-pollinated by bats. The growers prefer to plant saplings in neat rows They prune them to control the bug and strengthen the root. One man with a machete can prune 2,000 plants in a day, even though each has about 200 6ft spines, each looking like the blade of a saw.

The plant takes eight to 12 years to mature, at which point its huge root, resembling a pineapple but up to 500lb (225kg) in weight, is excavated. Smoky tractors and pick-up trucks haul loads of the roots to about 20 distilleries, which make several types of tequila.

In Tequila, I visited the original Jose Cuervo distillery, one of the two big producers, which claims to have made the first commercial tequila in 1795. Behind the distillery's Spanish mission facade, a cloistered courtyard, set round a fountain, is home to a caged raven - the cuervo.

The distillery softens the agave roots for 50-72 hours in steam ovens, minces them in a huge mill, then places the pulp on a sieve and washes out the plant's complex sugars. The resultant liquid is fermented with a yeast from the spines of the plant, and distilled twice in pot stills similar to those used to make cognac or malt whisky.

Jose Cuervo's has six well-worn, rocket- shaped stills made of copper and two modern ones of stainless steel. The small independent distillery that makes Torada tequila boasts a 48-year-old mill, but its stills are all stainless steel.

Tequilas labelled '100 per cent agave' should contain no other fermentable sugars. By law, 51 per cent agave is the minimum, but the remainder may be made up from cane or other sugars.

The cheaper, colourless tequilas are matured for only a few weeks. Others may be coloured, and softened in palate, with caramel or almond essence. Those labelled Reposado have been matured in oak tanks for up to six months. Those with the appellation Anejo have been kept for at least a year, often two or three and occasionally eight or 10, in oak barrels usually obtained from Kentucky bourbon distillers. (Casks of the same origin are used by some distillers of malt whisky).

Producers of tequila, like their whisky counterparts a decade or so ago, have no specific words to describe the aromas and flavours of their product; instead, they make bland comments about a good tequila being smooth or well balanced.

Is it the agave's appearance that suggests to me a flavour of artichokes, or a hemp-like, hessian aroma, or a touch of resiny pine? Some tasters use such descriptions as dill, broccoli and cucumber.

At London's top tequila-tasting spot, Cafe Pacifico (5 Langley Street, Covent Garden, 071-379 7728), the head bartender, Danny Smith, believes that the spirit of tequila manifests itself even through the orange liqueur added to make the Margarita cocktail, the sparkling wine of a macho 'slammer', or the rituals of lime-biting and salt-licking. Given the choice, he prescribes Cuervo's super-premium version 800, which I find has a lot of flavour development and a lively, peppery finish.

The principal tequilas of Cuervo's main rival, Sauza, are on the sweet side for my taste, though I very much enjoy its drier, almost herbal, premium version, Bornitos (100 per cent agave). Sauza's more venerable Tres Generaciones has a big bouquet, a crisp palate and a long finish.

The other big tequila, Herradura (100 per cent agave in all versions), seems firmer and spicier, with a suggestion of chillies. El Tesoro Muy Anejo is robust and resiny, with a suggestion of sherry.

And for complexity and delicacy, look out for Orendain Ollitas, with its fragrant bouquet and cachou-like palate. If you ask nicely, Cafe Pacifico will serve you this one in a snifter.

Here are some other tequila hot spots: Bristol, La Cantina, 1 Chandos Road (0272 744801); Liverpool, El Macho, 23 Hope Street (051-708 6644); Manchester, La Tasca, 76 Deansgate (061-834 8234); Glasgow, Cantina Del Ray, King Street (041-552 4044).

(Photograph omitted)