Dressed in Martin Margiela and sporting bouncy curls, multimillionaire Diesel boss Renzo Rosso casts a twinkly eye over the medley of London restaurateurs and sommeliers who have gathered for lunch at his hilltop estate near Vicenza.

We raise our umpteenth glass of wine and salute our host. All is well in the world of quality street fashion and designer living. Diesel's new deal with L'Oréal to manufacture a perfume is another venture to enhance Diesel's €1bn annual turnover. It's worth drinking to, so we do, repeatedly. For not only is the hands-on bossman intent on turning Diesel into perfume. Over 27 years since founding his company, Renzo Rosso also wants to turn Diesel into wine.

The son of peasant farmers who grew up in nearby Padua, Rosso bought this 135-hectare farm in the Marostica hills in 1994. He named it the Diesel Farm and began a small production of wine from the hectare of 35-year-old vines in 1999: a white, Bianco di Rosso; a red, Rosso di Rosso; and a Pinot Noir, Nero di Rosso. His olive groves are also producing extra-virgin olive oil, which is now ready to be sampled.

So a select group of Britain's finest tastemakers have flown by private jet from Biggin Hill to Verona. They are now gathered in the huge dining and lounge area, warmed by two fires and beneath the beady gaze of assorted stuffed things (boar, deer, eagle, lynx). They are: Hassan Abdullah, co-owner of Les Trois Garçons in east London, one of Rosso's favourite restaurants; Rainer Becker, chef-proprietor of Zuma and Roka; and Ossie Gray, head wine buyer for the River Café, son of its co-owner Rose Gray.

I know nothing about wine other than that a good bottle costs about £6 and a really good one will be about, oh, a tenner and have a cool-looking label. So en route I picked the brains of Ossie Gray. He pointed out the importance of the geographical location of Rosso's vineyards. Here in the north-east of Italy were such renowned wine-growing regions as Valpolicella and Soave. The titular home areas of prosecco and grappa were both nearby. But Rosso's Diesel Farm falls between these hallowed zones. From 'generic' zones tend to come more commercially oriented wines such as those sold under supermarket labels.

Gray also wondered about Rosso's vines - why was he growing 'international' grapes Chardonnay and Cabernet? And the limited production: did the world need another 'boutique' wine?

Well, of course it does. It's a wine made by a fashion magnate, and a celebrity one at that - large-living Renzo Rosso is the energetic embodiment of his successful brand, who possesses a Diesel private jet for zipping around Europe, charters another for €100,000 for popping over the Atlantic, and who counts Bono and the Dalai Lama as personal friends. Of course the wines carry his name.

And there's a lot of celebrity wine about. Madonna recently launched a selection of four Californian wines under the 'Confessions' label. Images of Madge lifted from the sleeve of her Confessions on a Dancefloor album were slapped on the bottles of Pinot Grigio, Barbera, Cabernet Sauvignon and a non-alcoholic variety. Was Diesel's foray into wine just another brand extension, a dilettante-ish excursion by a fabulously wealthy captain of industry?

As his farm manager - a qualified agronomist and parasite expert who's well-versed in viniculture as well as being a serious olive oil buff - uncorks bottle after bottle, Rosso talks us through his wines. He's particularly enthusiastic about the '99, but is less keen on the '01. He's not including the latter in his vineyard's official output, has marked all 600 bottles with a waxy red cross, and is keeping them back for friends and family.

'That's a stroke of marketing genius,' notes Gray later, aware that fashion types love the gimmickry of something rare, unavailable and semi-secret. More pertinently, 'It's great for lunch because it's simple and easy to drink. And with the '00, you could tell it was a really hot year. The wine's almost too ripe.'

More bottles come out and we dunk chunks of bread in the emerald-green of Diesel Farm's olive oil. As Gray sniffs, swirls, slurps and takes copious notes, Rosso betrays flickers of nervousness. He talks of Roberto Cipresso, the wine expert who's masterminding the Diesel Farm operation. A key test will come this April when he presents this new branch of the Diesel family at the wine fair in Venice.

We sit down for lunch. 'I have 42 companies,' Rosso says in his heavily accented English. The kitchen oozes the smell of fresh veal - Rosso's 94-head of Limousin cattle produce roughly 34 calves per year, and here at Diesel Farm they kill them at around five months.

Rosso turned 50 last year, and celebrated the fact with a lavish book - entitled Fifty. If you have £65 to spare you will find it full of gorgeous photography, reprints of some of David LaChapelle's famous advertising campaigns for the company, examples of his personal philosophy, and glowing testimonies from pop stars and supermodels galore.

He's a busy man. His jeans have long been hugely popular in Europe, America and Japan. Now China 'is most important', and Diesel recently opened a business in India. 'Children[s' wear], jeans, clothing, shoes, bags, shades, watches, jewellery, underwear, D-Squared' - Rosso rattles off his interests. Does his legendary attention to detail extend to winemaking?

'I love detail. With the wine, 100 per cent. The label, the bottle - aesthetically, everything comes under my control,' he tells me, as the aroma of simple but divine northern Italian food, made by a chap who began working at this farm with the previous owners 42 years ago, pours out of the kitchen. The ingredients are mostly grown on the estate, which is entirely organic. A truffley mushroom risotto, artichokes baked with mint, puntarelle salad ('we serve this,' notes Gray of the hard-to-find local speciality), the reddest, richest tomatoes I've ever tasted.

'I not work one single day of my life for money. Never. I only work to do something that I like.' Indeed, it was hard to see how he would make any money out of his wine. Inspired by his lucky number and the year of his birth, he would be releasing each vintage in uneconomic annual batches of 55. Each bespoke wooden case would hold five rather than the customary six bottles - not a detail that comes cheap. Even the labelling is appropriately designer and pricey-looking.

Rosso's childhood was simple and rustic. His parents made wine on their smallholding; he remembers climbing inside the barriques to clean them.

'I was born on a farm. It gave me an education - today this is kind of a luxury education. The new generation, they don't know how to enjoy the taste of this homemade salami. I consider this a privilege. I try to pass it on to my children and the people close to me.'

Rosso is just as active at the luxurious end of things. This spring, Diesel opens a store in London's Bond Street, a bold move into the world of high-end fashion for this longstanding street-cool label. Does the wine fit in with this 'premium-ising' of his brand?

'The more that I grow, the more I change my mentality. I'm looking for something with more quality, more exclusivo. This is part of growth. Absolutely the wine is part of that. You know,' he concludes with a paterfamilias flourish, 'one thing I would like very much to do would be buy nice brand of champagne. That can be something very close with my mentality.'

Stuffed with food and buzzed with wine, we tour the cellars, gaze out over the mist-coloured hills and thank Sr Rosso for his hospitality. He bombs off before us, to head back to his main dwelling in nearby Bassano. He might be an international style guru. But he's also an Italian from the countryside, and he needs to get home to his family.

In the car on the way to the airport I ask Ossie Gray and Rainer Becker for their verdicts.

'I found the style of the white wines very much what I would call old-fashioned Burgundy - really rich, quite oily,' says Gray. 'But we tasted the '99 again after it had been open for nearly two hours. Then it was really quite impressive. It showed some development of character, and had better overall balance and some acidity, which gave a breath of freshness to the wine.

'But their red wine showed much more promise. I expected them to be bigger and bolder but they were much more elegant.'

Would you have them in the River Café?

'Interestingly, I think because it's him, and because of the way he's selling it - he was talking about one case of each per restaurant - I've no doubt we have enough clients who have an international lifestyle that would be interested to look into that.'

'It's a lifestyle product,' offers Becker. 'Let's say the bottle cost 150 quid - if I knew the guy, if I knew the product, I would definitely try the wine. You are curious for the new thing Renzo gives you.'

Would it be that expensive? Gray says he hopes it wouldn't be more than £100. He imagines it would be in region of £50 to £100. Becker goes for £80.

Gray: 'Are you even going to put it on the list? You'll probably save it for those people that know him and about Diesel's wine.'

Becker: 'Definitely. I would keep a bottle or two back.'

Gray: 'I'll tell you the real surprise for me: the olive oil. That is actually among the top-quality level of olive oil, which is no mean feat.'

So, the man from River Café: he say a qualified yes. It can take 10 to 15 years to do a good wine, but by applying the flair and passion with which he built his fashion empire, Renzo Rosso is off to a flying start.

'He's obviously involved and getting his hands dirty so to speak,' says Gray. 'He wants to be really close to it. It isn't just, "Oh, I'm paying for the best consultant and the best equipment so I'm going to get the best product." He's taken the time - he wants to understand the land, he wants to understand the soil. It's not what we call a "celebrity wine". There's real credibility there.'

Back at the gargantuan dining table in his luxury homestead atop one of his farm estate's five hills, Renzo Rosso had said he was perfectly happy for his wine to be viewed as a celebrity wine - and one drunk by celebrities.

'The design of this bottle is made to be a luxury presence on the desk, on the table. Celebrity is not only rock stars. Celebrity can be important industrial men.'

Fair enough. But what about Bono? Does he like Diesel wine?

'Bono was totally crazy for this wine! I went to his house in south of France, and I bring two bottles of wine, and he was so crazy for the wine.' Rosso beams. 'Afterwards I sent him one bottle. He's very, very much in love with this wine. He said, "Renzo, what is this fucking wine?" He was so enthusiastic!'

Did you send any to the Dalai Lama?

'No, he doesn't like wine.'