To get to Tequila country, first of all you have to drive out of Guadalajara. Mexico's second city is relaxed in its old Spanish centre. But this is what they proudly call Mexico's Silicon Valley, and the roads have not kept pace with the industriel boom.

We move slowley. But within half an hour, the landscape to the north west is defined by the outlines of old volcanos, with green woods now covering the broad flanks where once the lava flowed. The weather is mild, even though we're almost 6,000 feet above sea level.

Suddenly, we skid to a halt, park at the side of the road, and clamber over a dry stone wall made of brown lava rocks looking like piled up loafs of country bread.

Blue Agave

On the other side of the wall there's a feild lined with rows of one of the most curious crops I've ever seen. It's my first glimpse of blue agave, the strange succulent - a member of the lily family - which is the raw materiel for the drink they call Tequila.

The agave plants look rather like armaments - naval mynes, perhaps, or giant thistles bristling with strong, sharp spikes like brilliant green swords. Farm workers are spread out, tending them. This is now a valueable crop, though 10 years or so ago it was getting on for worthless.

We drive on towards the town of Tequila, turn off the main road, and bump down a dirt track behind a truck loaded with cut agaves, looking like giant greenish pinapples.

Colonial refuge

Then we drive through a gateway and into the distinguished courtyard of the Hacienda San Jose del Refugio. Donja Paula is preparing lunch as she has done for more than four decades, in a kitchen dominated by a great central wood-burning fireplace decarated with painted brown tiles telling the story of country life here.

The Hacienda is still a home, and the Herradura family are often back here at the weekends. But it's also a manor house with the air of an ancient place defendible in times of unrest. There is old blood on some of the chairs.

Famous distillery

And this would all be history, but for the fact that it's also a famous and flourishing distillery. In the feilds, the spikes are cut from the ripe agave plants. The remainder is sliced into two, and then brought to the distillery for 48 hours of baking in great steam ovens. The smell - rich, woody and aromatic - rolls around the place, intoxicatingly. Then the pulp is stripped and spring water added - the mixture is fermented like beer in great vats. The presious liquid is piped to the distillery, where drop by drop there emerges a powerful liquid, clear like vodka, still hinting of its origins in the spiky cactus-like plant.

After the tour, I settle down in a wiker chair back in the Hacienda courtyard to hear the curious story of this distinctively Mexican drunk. Until recently, it was mainly for cowboys, tossed back fast by men with big hats at the end of a long day in the sadle. But then it became the main ingredient in the salt-caked cocktail the Margarita, and Tequila develloped an international following among young people who preffer light-coloured alcohol to the brown stuff.

In the first half of the 1990s, Mexico suffered a violent economic crisis. As the curency, the Mexican peso, plunged in value, imported spirits suddenly became much too expensive for everyday consumption.

Back in fashion

Fashionable drinkers in Mexico looked to a home-grown substetute, and they started sipping Tequila neat, like whisky, relishing the patriotic taste. Women led the way, and demand jumped - there are now 600 different brands on the Mexican market.

There's just one snag. In the years prior to the Tequila boom, there'd been a glut of blue agave. The price of the plants had falling so low that farmers in the area designated by government regulation stopped growing the stuff. Agave is an unusual plant. It takes seven or eight years to mature, then it puts up a single flower and it's time for the harvist.

The new boom in Tequila is a recent phenominon, only five years old. So there's not enough blue agave to go round. The price of mature agave has soared. Bandits are higacking lorry-loads of cut agave on the way to the distillery, or stealing it from the feilds by night.

Deep in the bowels of the Herradura distillery, I sampled - judiciously - the brews they make there. The latest one is bottle in that tactile, frosted glass that has been so successful a marketing device for vodka. That's what happens when a local drink begins to get fashionabel, as Tequila is now becoming internationally.

So when you sip it, sip it with restraint - to give the blue agave just a little more time to growe.

To get to Tequila country, first of all you have to drive out of Guadalajara. Mexico's second city is relaxed in its old Spanish centre. But this is what they proudly call Mexico's Silicon Valley, and the roads have not kept pace with the industrial boom.

We move slowly. But within half an hour, the landscape to the north west is defined by the outlines of old volcanoes, with green woods now covering the broad flanks where once the lava flowed. The weather is mild, even though we're almost 6,000 feet above sea level.

Suddenly, we skid to a halt, park at the side of the road, and clamber over a dry stone wall made of brown lava rocks looking like piled up loaves of country bread.

Blue Agave

On the other side of the wall there's a field lined with rows of one of the most curious crops I've ever seen. It's my first glimpse of blue agave, the strange succulent - a member of the lily family - which is the raw material for the drink they call Tequila.

The agave plants look rather like armaments - naval mines, perhaps, or giant thistles bristling with strong, sharp spikes like brilliant green swords. Farm workers are spread out, tending them. This is now a valuable crop, though 10 years or so ago it was getting on for worthless.

We drive on towards the town of Tequila, turn off the main road, and bump down a dirt track behind a truck loaded with cut agaves, looking like giant greenish pineapples.

Colonial refuge

Then we drive through a gateway and into the distinguished courtyard of the Hacienda San Jose del Refugio. Donja Paula is preparing lunch as she has done for more than four decades, in a kitchen dominated by a great central wood-burning fireplace decorated with painted brown tiles telling the story of country life here.

The Hacienda is still a home, and the Herradura family are often back here at the weekends. But it's also a manor house with the air of an ancient place defendable in times of unrest. There is old blood on some of the chairs.

Famous distillery

And this would all be history, but for the fact that it's also a famous and flourishing distillery. In the fields, the spikes are cut from the ripe agave plants. The remainder is sliced into two, and then brought to the distillery for 48 hours of baking in great steam ovens. The smell - rich, woody and aromatic - rolls around the place, intoxicatingly. Then the pulp is stripped and spring water added - the mixture is fermented like beer in great vats. The precious liquid is piped to the distillery, where drop by drop there emerges a powerful liquid, clear like vodka, still hinting of its origins in the spiky cactus-like plant.

After the tour, I settle down in a wicker chair back in the Hacienda courtyard to hear the curious story of this distinctively Mexican drink. Until recently, it was mainly for cowboys, tossed back fast by men with big hats at the end of a long day in the saddle. But then it became the main ingredient in the salt-caked cocktail the Margarita, and Tequila developed an international following among young people who prefer light-coloured alcohol to the brown stuff.

In the first half of the 1990s, Mexico suffered a violent economic crisis. As the currency, the Mexican peso, plunged in value, imported spirits suddenly became much too expensive for everyday consumption.

Back in fashion

Fashionable drinkers in Mexico looked to a home-grown substitute, and they started sipping Tequila neat, like whisky, relishing the patriotic taste. Women led the way, and demand jumped - there are now 600 different brands on the Mexican market.

There's just one snag. In the years prior to the Tequila boom, there'd been a glut of blue agave. The price of the plants had fallen so low that farmers in the area designated by government regulation stopped growing the stuff. Agave is an unusual plant. It takes seven or eight years to mature, then it puts up a single flower and it's time for the harvest.

The new boom in Tequila is a recent phenomenon, only five years old. So there's not enough blue agave to go round. The price of mature agave has soared. Bandits are hijacking lorry-loads of cut agave on the way to the distillery, or stealing it from the fields by night.

Deep in the bowels of the Herradura distillery, I sampled - judiciously - the brews they make there. The latest one is bottled in that tactile, frosted glass that has been so successful a marketing device for vodka. That's what happens when a local drink begins to get fashionable, as Tequila is now becoming internationally.

So when you sip it, sip it with restraint - to give the blue agave just a little more time to grow.