On board his ocean-racing yacht Foncia, Michel Desjoyeaux was making his final preparations on Friday evening for the Vendée Globe, the toughest race – bar none – in all of sport. A few feet away from where we were chatting, hundreds of onlookers were packed 12 deep on the pontoon in Les Sables D'Olonne, a port in western France. Desjoyeaux, a 43-year-old Breton, is a god in these parts.

The race started on Sunday. Yesterday, the fleet had already hit big trouble in the Bay of Biscay, with a 50-knot storm threatening to wreak havoc on the 30 competitors, seven of whom are British – an unprecedented number.

When Ellen MacArthur finished second in the Vendée Globe in 2001, becoming a national treasure, Desjoyeaux was the man who beat her to first place. Between 2001 and 2004 he consecutively won the world's three most prestigious solo races: the Vendée (around the world), the Route du Rhum (Brittany to Guadeloupe) and the Transat (Plymouth to America), earning the tag "the most honoured yachtsman on the planet".

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So what does the Vendée Globe mean to this titan? "It is the only race around the world alone, without help, without stop," he told me. "For three months. That is everything you need to know."

By midday yesterday, Desjoyeaux had already been forced to turn back to Les Sables D'Olonne, having sustained a leak. The race rules allow no shore stops but any boat sustaining damage in the first 10 days can return for repairs, before trying to make up the time deficit.

As the wind gathered and the seas swelled in Biscay last night, several other skippers were heading back. Fingers were crossed that fleeing for safety was as dire as things got.

The Vendée Globe organisers call it the "Everest of the seas". In fact, conquering the mountain has proved easier, and in recent years, safer. There have been around 4,000 ascents of Everest. It is not unusual for a fit adult to reach the summit on a corporate trip. The Everest fatality rate since 1990 – the year the first Vendée ended – is 4.4 per cent. Even space travel is much more common than sailing solo around the planet. Some 485 people have been to space, and the fatality rate for space flights is 3.7 per cent (or 18 people).

Only 60 people have ever sailed around the world solo non-stop. Of those, 41 have done it in the quadrennial Vendée Globe (some more than once). Of 67 different people who had tried the Vendée before this year, three have died while doing so: the USA's Mike Plant and Britain's Nigel Burgess in 1992, and Canada's Gerry Roufs in 1997. The Vendée's fatality rate is 4.5 per cent.

Its failure-to-complete rate has varied. In 1996-97, in a race marred by Roufs's death and by four other skippers being capsized (Tony Bullimore among them), 10 of 16 starters (or 63.5 per cent) failed to finish.

Yet despite the Vendée Globe's dangers, cancelling because of any death at sea would be counter to the philosophy that underpins the competition: a skipper and a boat versus nature. Getting round is the aim. Winning is icing on the cake.

Jonny Malbon did not enter expecting to win, as the 34-year-old from Cowes confided on a tour of his boat Artemis, in Les Sables. He has 100,000 miles of competitive sailing on his CV. He worked as a senior sailor alongside Ellen MacArthur for a time, but this Vendée is the first solo race.

Certain aspects of the trip hold no allure. That was obvious as we hung out together during an ascent of his boat's 95ft mast. "I really, really don't want to be coming up here during the race," he said. "At all." It is easy to see why. We were docked, on calm water. It is terrifying to imagine climbing the mast in bad weather; impossible to envisage then achieving anything practical, like a repair.

Why is Malbon competing? "Natural progress," he says. "I've been offered an opportunity of a lifetime. It's daunting, but I did the hard part just getting to the start line."

He has had little time to get used to his boat – one of 20 built for this race. A skipper would expect to spend six months making checks with a crew, easing towards sole control of these hi-tech machines that can cost £3m each. But Artemis was four months late out of the shed, then had mast problems. So Malbon's first taste of handling her alone was a 4,000-mile qualifying passage to Newfoundland and back in August.

"It was the most amazing and most frightening thing," says Malbon. "Halfway through, I thought 'You're mad, why are you doing this?' On your own, things can go wrong suddenly, and badly."

French skippers have dominated the race, winning all five "editions" to date. They have also filled 13 of the 15 podium places, interrupted only by MacArthur (second in 2001) and Mike Golding (third in 2005). The French take pride in their dominance, partly because many of France's best sailors hail from Brittany, where romantic notions of seafaring dominance are ingrained. A race like the Vendée is driven by corporate money, and when sails alone can cost £300,000 per set, you need that backing. But each boat relies on the ability of its skipper, the hero figure at the heart of each individual Vendée story.

"That's what the magic is," says Loick Peyron, a veteran 49-year-old former runner-up, aboard Gitana Eighty this time. "If you say to a four-year-old child, 'There's a man on a boat who's making a trip around the world', they'll understand. Then, if you tell them that there are albatrosses and icebergs, and if they know some of Jules Verne's stories, well, that's the magic."

Malbon expands on the mental challenge of being alone, a situation he endured for a mere 21 days in his qualifier. He will sleep in 30-minute bursts for perhaps four hours each day. In the first week, amid coastal traffic and storms, sleep will come in spells of up to 10 minutes at a time.

He will eat freeze-dried stews three times a day, made palatable by garlic and chilli sauces. His concession to luxury will be the occasional boil-in-the-bag beans and bacon for breakfast. He will consume two carbohydrate shakes a day, eat three small bars of chocolate, have three cups of tea with two sugars and a small bag of dried fruit. His entire food stores, for a projected 95 days at sea, weigh 110kg.

Malbon will also talk to himself, often and out loud. He will address his auto-pilot as "matey": "I talk to myself anyway. I think that's quite normal."

Through tiredness, he will hallucinate, as he did during his qualifier. "There's a camera box outside on the deck. One night, very vividly, it looked like someone I know from Cowes. I clearly knew he was not on board, and I knew he couldn't fit inside this tiny little box. But it was perfect outline of him. You imagine things. It's part of the ride."

The "ride" will last for 26,000 miles down through the Atlantic, around the Cape of Good Hope, through the Southern Ocean below Australia, round Cape Horn and back to Les Sables.

The race's principal backer is the region of Vendée. There is a €490,000 (£400,000) prize pot (€150,000 to the winner) but much more is spent on safety, on the tented race village that will host more than a million spectators, and on insurance. More than 300,000 turned out to watch Sunday's start, screened live on the 1pm news.

""But to get in a boat and sail the world, that is not an option for most, who can't or don't want the risks. Through us, they dream," says Desjoyeaux. The public on the pontoons backed him up. "These guys are heroes," Aurelie Bigot, 28, from Rennes told me. Guillaume Legué, 33, added: "This is more important than the Tour de France."

For Britain's Steve White, 35, a father of four from Dorchester who is competing on a relative shoestring budget, finishing would be a triumph. He mortgaged his house three times to buy his £300,000 boat. At the last minute he renamed it Toe in the Water after a charity for badly injured servicemen following an anonymous donation.

White's total campaign spend will be £500,000, boat included, against up to £10m by other teams. "It's pretty weird, slightly surreal," he told me as hordes of locals scrambled for his autograph. "I'm just Steve from Dorset and I'm getting mobbed by schoolgirls."

His supplies, unlike those streamlined cargoes of the pros, arrived at the dockside in seven shopping trolleys and included sacks of porridge and tins of beans and syrup. White's sweetest moment would be getting to the end in one piece.

Michel Desjoyeaux has been impressed by some of the flashier British boats. "It's possible that a Briton could win," he says. "We wouldn't appreciate it. But it's possible."

When the storm subsides, we may have a better idea of whether that remains the case.