Susan Lewis is sitting in the drawing room of Villa le Trident, built on the steep red rocks above the Bay of Cannes, turning the pages of her late great-uncle’s guest book. It is full of sepia-toned photographs from the 1920s, 1930s and 1940s. Almost all show well-bred young men in scanty bathing trunks, posing on the rocks or diving into the sea. There is scarcely a woman in sight.

The great-uncle in question was Eric Sawyer, a former British army officer, who was both the business partner and boyfriend of Barry Dierks, a pioneering American architect who built more than 100 villas on the Côte d’Azur in the years after the first world war. Le Trident, completed in 1926, was not only Dierks’s first project and his own home, it was also the ultimate Mediterranean hangout, where the likes of Pablo Picasso, Somerset Maughan, Beverley Nichols and the Duke and Duchess of Windsor would gather to party.

“Eric and Barry were the darlings of the coast,” says Lewis, 55, a furniture designer turned bridge teacher. “They were friends with Picasso and did Villa Mauresque [on Cap Ferrat] for Somerset Maughan. Edward and Mrs Simpson came to stay here; we’ve got their signatures in the book.

“When the fleet came in they had parties on the roof and invited all the sailors over and had a ball. It must have been such a freedom for all the English people who had to behave totally differently back home and were able to come down here and be completely themselves. It was such a happy place.”

The house, which Lewis and her family are now reluctantly selling for £17.5m (“We need the money,” she admits frankly) served as a show home for a new style of architecture that Dierks brought to the Côte d’Azur. A graduate of the Carnegie Institute of Technology in Pittsburgh, he studied architecture in Paris in 1921, which was where he met Sawyer, who was working in a bank.

Family legend has it the pair were drinking one day in their usual haunt, the Ritz hotel bar, when the barman urged them to eavesdrop on a loud conversation between an American and his chauffeur. The man was the brother of Charles Dawes, recently appointed director of the US Bureau of the Budget, who had devised a programme to help rebuild the shattered German economy. The pair piled all their savings into the American companies that stood to benefit and made a quick profit. And so it was, with more money from Eric’s mother, they travelled south, bought 1½ acres of spectacular seafront land and built the three-storey villa.

Up until then, many of the houses commissioned by the British and other wealthy overseas buyers who colonised the south of France had been solid, square, belle-époque affairs designed for winter living. Dierks’s designs were more open and Californian in style, with rows of french windows and balconies aplenty – ideal for the new fashion for summer tourism.

Le Trident exemplified this style: the tone is set by the airy drawing room, which gives onto terraces on three sides, from where there are spectacular views eastwards over the Bay of Cannes and westward over an unspoilt coastline to the Cap Roux headland. The house, which spans 385 sq metres, also has a dining room, seven bedrooms, five bathrooms and a huge roof terrace.

Dierks was a stickler for detail, designing several pieces of furniture, including bookcases and a large sharkskin-covered occasional table, specially for the villa. He also positioned the dining terrace in such a way that by 1pm it was always in the shade. (What he couldn’t predict, however, was that France would change time zones in the 1950s, meaning modern diners must wait until 2pm.)

Le Trident suffered during the second world war, when southern France was occupied, first by the Italians and then the Germans. Dierks was initially active in the Red Cross, but once the Germans arrived, he fled with the housekeeper, chef and his beloved dogs to Britain. Sawyer, by contrast, was active in the resistance, rowing fellow fighters out to the allied submarines in the bay. A gilt mirror inside the hallway still has a hole from the German bullet that shattered it. Outside the front door, a plaque hon-ours his work fighting the Nazis.

It took until the early 1950s to return the house to its former glory. Give or take a bathroom or two, it has remained much the same since. Dierks died in about 1960; Sawyer survived until 1985, bequeathing the property to Lewis’s father, Ralph, who, she says, was the two men’s “surrogate son”. He, in turn, passed it on to Lewis and her brother.

For Patrick McCrea, a British estate agent who has sold high-end properties in the south of France for more than 25 years and counts Chelsea boss Roman Abramovich, advertising mogul Lord Saatchi and singer Rod Stewart among past clients, it is not so much Le Trident’s style as its location right on the waterfront that will be its main selling point.

“This house hasles pieds dans l’eau, literally your feet in the water – direct sea access,” says McCrea. “It’s virtually impossible along this coast. In Cap Ferrat, for example, you’ve got a path all the way round, and in Cap d’Antibes, almost of all of it has a road around it. If you go further along to St Tropez, only two houses have their own private beach – one of which is Mohamed al-Fayed’s. This privacy, contact with the sea and geological rock formation make a combination that is very difficult to find.”

The placing of the house on the market for the first time in its life follows a decade-long property boom on the Côte d’Azur. Although, as elsewhere, the mainstream market is slowing, the top end continues to flourish, fuelled by an influx of Russian buyers, whom McCrea estimates account for three-quarters of sales above €10m (£7.9m) – helping prices of the more expensive properties triple over the past decade.

“The places the Russians would look at are Cap Ferrat, Cap d’Antibes and St Tropez, in that order,” says McCrea. The trend was set by Abramovich, who reportedly bought the Chateau de la Croë, once home to the Duke and Duchess of Windsor, at the beginning of the decade for £15m, and fellow oligarch, Boris Bere-zovsky, who is thought to have paid a similar amount in the 1990s for Chateau de la Garoupe, an even grander waterfront mansion nearby.

Such transactions, often made through companies, remain shrouded in secrecy. Certain details, however, do leak out: those familiar with the local market cite a villa on Cap Ferrat once owned by Andrew Lloyd Webber and latterly by Gordon Crawford, founder of London Bridge Software, that was on the market for three years at £99m before selling recently to a Russian for what is believed to have been £67m. Crawford is thought to have bought the property a decade ago for about £15m.

So is Le Trident likely to go to a Russian, too? McCrea doubts it – not only because of the villa’s distinct lack of bling, but also because of the location. “If this had been in Cap Ferrat, I could have sold it to a Russian for three times the amount in half an hour,” he says.

The eventual purchaser, he believes, is more likely to be a Briton or Irishman, keen to restore Le Trident to its former glory. Whether they manage to live in the same flamboyant style as its original owners remains to be seen. +Le Trident is for sale for £17m through Savills International (020 7016 3740, www.savills.co.uk/abroad ) and Armstrong McCrea Associates (0780 075 0156)

GET YOUR CÔTE

St-Jean-Cap-Ferrat £20.7m Situated within walking distance of the village and beaches, this recently renovated 600-square-metre villa is set in 1,700 square metres of grounds, with 360-degree views of the Mediterranean. It has several reception rooms, seven bedrooms and a large infinity pool (Savills International; 020 7016 3740, www.savills.co.uk/abroad )

St Tropez£9.6m A 480-square-metre villa set on a 6,000-square-metre plot close to the centre of the town, with four receptions, six bedrooms and bathrooms, a summer dining room, swimming pool, tennis court and boules area. There is the possibility of a 400-square-metre extension (Knight Frank; 020 7629 8171, www.knightfrankinternational.com )

Juan-les-Pins£1.6m-£27.8m Looking for a lock-up-and-leave alternative? Le Provençal, an art deco former hotel, is being converted into 56 luxury flats, ranging from 80 to 700 square metres. It will have a pool, games room, 24-hour concierge service and state-of-the-art security. (Savills; 020 7016 3740, www.savills.co.uk/abroad )

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