He may be the founder of a global advertising giant, but Sir John Hegarty has another venture to pursue. For the past six years the man from Bartle Bogle Hegarty (BBH), who was behind a famous Levi's jeans campaign (the one where Nick Kamen strips off in a launderette) has been building up his vineyard in the South of France.

“I've worked in advertising for 40-odd years. I deplore the word retire, but you want a segue [a seamless link] into doing something else,” he says. “We didn't want to just have a house in the country where we went once every four to five weekends, opened it up, read some papers, closed it up on the Sunday, and drove back.”

After being convinced by Roy Richards, a wine-importer friend, of the potential of Languedoc-Roussillon, the largest vine-growing region in France, Hegarty, 63, and his partner, Philippa Crane, 52, bought Domaine de Chamans, an old farmhouse set in 22ha (54acres) of vines in Trausse-Minervois, in the foothills of the Montagne Noire near Carcassonne. They bought the plot through Vignobles Investissement, a vineyard specialist in Montpellier with a large British clientèle. A similar property is now for sale through the agent for £1.74 million.

Crane, a former board member and ad producer at BBH who now manages the vineyard full time, and Hegarty, who was knighted last year, found the place after viewing only three properties in the region. “We envisaged going there once a month for about a year, but we saw this rundown farmhouse and cave. It was cold and rainy, so it wasn't selling itself to us, but we both felt that it was very special and had a magical quality to it,” she admits.

But the choice was not purely whimsical. Adam Dakin, of Vignobles Investissement, insists that, out of the 200 vineyards on the market at the time, Domaine de Chamans was in the top ten. Factors such as the vineyard's south-facing slopes, the direction of the wind and the quality of the soil made it a sound investment, he says. Crane comments: “Vignobles Investissement gave a proper analysis of the soil to make sure that there was no disease.”

For the previous 35 years the grapes from Hegarty's land had been sold to the local co-operative. But Dakin says that investors will not make much money by selling to the co-op, nor will they become rich by selling wine in bulk to be blended with other wines. So the couple set up their own label and now produce their own award-winning Minervois wine, Hegarty Chamans. Their range of red wines is available at Oddbins and Adnams, from £7.29 to £11.99.

“We decided we had to do it ourselves or not at all,” said Hegarty. “We could have found a vineyard that was already making its own wine, but it wasn't right. The downside is that we had to establish a product from scratch as opposed to working with a product already being made that we could develop. But the upside was that we could make it our own vision.”

The couple hired Samuel Berger, an established French winemaker, to produce the wine. Meanwhile, they also engaged Peter Glynn-Smith, a British architect, after seeing the results of a friend's barn he converted in Gloucestershire. Now based in France and using local labourers, Glynn-Smith has helped to realise their vision of the farmhouse complete with sunken pool and ultra-modern fixtures and fittings.

A venture of this type needs plenty of capital. Richard Edds, of the French property consultant Leisure and Land, says that you would need to spend at least £500,000 to renovate a vineyard and make it profitable. Dakin agrees. “The majority of people do this for the lifestyle,” he says. “They don't care if it makes money. You'll find that people like Sir John come in and will modernise and improve the cave with automatic cooling systems and computers, which all costs a huge amount of money. It takes time to get your money back.”

But for Hegarty it has been worthwhile. “It's such an expensive industry to set up,” he admits. “Also it's over-supplied and it takes a very long time to develop the product that you want to make. If you are dealing with an agricultural product you're subject to the vagaries of Nature. It's not like making jeans. At the beginning you are a farmer, then you're a chemist, and, if you are selling your wine, you're a marketeer. But nothing great is created with ease.”

The couple now spend about one weekend a month enjoying the fruits of their labours and insist that there is nothing more satisfying than sharing a glass of their wine with friends in the vineyard where it was made.

Vignobles Investissement: 00 33 467 225552, vignobles-investissement.com Leisure and Land: 020-8952 5152, leisureandland.com

For Sale: A French vineyard

This vineyard in the foothills of the Cévennes mountains in Languedoc-Roussillon costs £2.2million. The 75ha (185-acre) plot has a 27ha vineyard, a three-storey stone house in need of renovation, and a traditional cellar. More details: Vignobles Investissement.

Times recommends

• Spanish property: why it's crunch time on the Costa del Sol
• Strong Euro and credit crunch impact overseas property buyers
• How to find the perfect Paris pied-a-terre