Nearly 20 years ago, two events occurred in the life of perhaps the world's most famous winemaker, Michel Rolland. He met luxury goods tycoon Alain Dominique Perrin and he went to Argentina.

Rolland has maintained his connection with both and there is one common factor - Malbec. More readily associated with Merlot and Cabernet thanks to his consultancies in Bordeaux, Rolland has spent years observing one of the Médoc's all-but forgotten varieties in the sun-baked vineyards of Mendoza and the rolling hills surrounding Cahors in south west France.

He's uniquely placed to analyse the similarities and differences , having helped Perrin to elevate Château Lagrézette in Cahors from obscurity to international fame . At the same time, he has worked with Argentinian producers to exploit what has become that country's signature grape, masterminding the establishment of the Clos de los Siete project with some of the leading wine families of Bordeaux.

So what are the differences and similarities?

First things first: Rolland is in no doubt about the intrinsic quality of the varietal. He says : "A good grape is a grape able to produce good rosé wine, light but fruity elegant wine, quite big wine or very smart wine like Pigeonnier [Lagrézette's top wine]. That's a good grape."

And, despite first appearances, tiny Cahors and the vast wine fields of Argentina have more in common than you might think. For a start, they share a more continental climate than Bordeaux - important for a grape that likes dry conditions.

"Malbec doesn't like Bordeaux because Bordeaux is often rainy and Malbec doesn't like rain," says Rolland. "That's why we pulled out almost all the Malbec from Bordeaux."

In Rolland's early encounters with Malbec in Argentina and Cahors he faced similar challenges. "The big problem in Cahors for years and even now has been over production. In Argentina, it is the same. We can produce 20 tonnes a hectare if we want - but the wine is awful."

The situation in Cahors was further complicated by a conservative, even reactionary, attitude to winemaking. Château Lagrézette's winery was only built in 1992, with earlier vintages outsourced - as Rolland remembers only too well.

"When I went to the co-op where Lagrézette was made, all the harvest was in one tank," Rolland recalls. "And we were fighting ..." He clenches his fists in mock aggression. "I told the Cave Coopérative to reduce yields. The guy was looking at me - what is this guy? This is a crazy guy ."

Years later, the association with Cahors is still uneasy . Perrin is clearly frustrated about the AOC rules governing Lagrézette and has spoken of his dream of turning the château into a kind of Vega Sicilia of the sud ouest, recognised as one of the top wines "in the Malbec world".

Lagrézette general manager Jean Courtois puts this in concrete terms: "We are talking about Lagrézette, Malbec, France, with the signature of Alain-Dominique Perrin. We are not really talking about Cahors."

Rolland agrees. "Malbec is really telling something to the consumer. Cahors stayed for years and years Cahors. The name was known in France, but nothing outside France. Now if we want to make the image bigger for Cahors, we have to give an identity, and the identity is Malbec more than Cahors."

As the man credited with the revival of Cartier, Perrin clearly has the wherewithal to cement Lagrézette's position at the top of the Malbec tree. He has recently bought 20ha of vineyards 15km from the château and he is considering a further e2 million investment in Lagrézette .

Such budgets are dwarfed by the investments in Argentina, with Rolland spearheading the huge Clos de los Siete project, to take one example. But he sees no conflict of interest or contradiction in championing the same grape variety on different sides of the world.

"The consumer is drinking Argentinian one day and Cahors the next," he says. "The trick is getting them to come back to the shop and take the bottle home again. "

And his personal favourite? Rolland takes refuge in the winemaker's traditional defence. "How can I choose between Malbec from Argentina and Malbec from Cahors? When you have children, you see how difficult it is to choose between them. I drink them both!"