Júlio Luís Maria is a fan of abattoir chic. Pointing to a bowed wooden table on which pigs were once slaughtered, he suggests turning it into a stylish garden bench. The ceramic dish into which the blood drained? An attractive bowl for bread rolls. Piled around him, awaiting domestic reincarnation, are old agricultural tools, peeling wooden doors and aged bed frames.

Senhor Júlio’s rustic bric-a-brac, strewn across his outdoor roadside emporium, has graced many of the world’s glossiest design magazines, upcycled for the hippy-chic restoration of old fishing and farming cabanas in fashionable Comporta. An hour south of Lisbon, the Alentejo region’s photogenic jigsaw of beach, pines and rice paddies has the breezy, barefoot, bleached-wood tang of the Hamptons or Uruguay’s José Ignacio.

While higher on the radar than ever before, Comporta’s laid-back languor has long attracted BCBG (bon chic bon genre) Parisians including Carla Bruni and Nicolas Sarkozy; well-connected Europeans from the Casiraghis to the Bransons; and art, design and fashion hotshots including Christian Louboutin, Mario Testino and Anselm Kiefer. In their wake came the mainstream A-list: Madonna, Gwyneth Paltrow, Harrison Ford.

The rarefied, paparazzi-free social scene is a big draw. But it’s not Comporta’s only trump card – far from it. The beach, for example, is astounding. Several stretches – Pego, Carvalhal, Aberta Nova – rub honey-hued grains, creating a seamless 37-mile long sweep of undeveloped sand. The second-longest beach in Europe after Lithuania’s Curonian Spit, it’s European in sensibility; southern hemisphere in scale.

Even on the weekends, busy with Lisboans, it’s capacious. Shift a few hundred metres and you’re alone. No wonder celebs feel safe to strip off. There’s zero danger of claustrophobia on the day I visit. At Aberta Nova I have the Atlantic to myself. ‘It’s just us and the fish,’ says tousled lifeguard Francisco, rubbing sunblock on his nose. ‘It was busier this morning.’

‘Really? How many?’

‘Two couples.’

To fully appreciate the beach, you don’t need Vilebrequin trunks or a Marysia swimsuit, you need a horse. Step forward José Ribeira, whose Cavalos na Areia stables offer memorable coastal rides. I slide aboard sleek, serene Caipirinha (my lift for the day) and navigate a verdant latticework of canals and rice paddies before rising through umbrella pines onto the dunes. An anticipatory hiss of waves and suddenly, there it is: the apparently endless beach vanishing into the heat haze to the north and south. Vast, empty, epic.

As we trot through gently frothing surf, José mentions a few famous guests including Shakira and Cristiano Ronaldo: ‘insurance was an issue’ (the latter’s legs are worth £90 million). He recounts meeting an amicable stranger admiring the dunes. They would, he told José, be perfect for his new, fat-tyre electric bike. ‘I built it myself,’ he explained, showing a phone photo. ‘I make things. My name’s Philippe. Philippe Starck.’

‘They’re famous, so what?’ sighs José. ‘Nobody cares. Nobody bothers them. They can relax and forget everything.’

This local insouciance is historical. Comporta is shorthand for the Herdade da Comporta: a private 31,000-acre estate – much of it protected national park – linking seven villages and hamlets including Pego, Brejos, Carvalhal and Comporta. It was bought by the Portuguese banking dynasty Espírito Santo in the 1950s, who alchemised old fishing cabanas into no-frills boltholes for the family.

Four decades on, they started selling land to minted European friends, whose visits provided a welcome summer boost to local coffers, while keeping things bohemian and basic. Security gates, CCTV, ostentation: it’s just not Comporta, chérie.

Espírito Santo went bust in 2014. Golf courses and construction are now in the pipeline, but the mood has (so far) been maintained. I drive along bumpy tracks past unpretentious white- walled Carvalhal and, before the dunes, spot a gaggle of low-level, thatched cabanas, their walls hooped with grass in the traditional vernacular: the holiday homes of a billionaire French entrepreneur, Swiss financier and German artist. The only signs of life are the ubiquitous storks, resplendent on vast nests. Nothing stands out. Nothing screams money.

This is, however, clearly no ordinary holiday destination. Comporta’s unassuming, white-and- blue-walled Mercearia Gomes, is dubbed “Little Harrods”. Shelves groan with duck, partridge and wild boar, along with Russian caviar, Pêra-Manca red wine and Dom Diogo olive oil. There’s Castelbel donkey’s milk soap, Paulo Tuna hand-forged kitchen knives and Mértola woollen blankets.

Naturally there are superb restaurants. Some of the best are wooden, windblown and stilted, overlooking the Atlantic. Nautically-themed Sal has widescreen-worthy views, sensational fish and celebrity clientele, while nearby Sublime Comporta Beach Club, all earthy hues, dried-reed décor and sun-dappled bamboo, serves lobster hot dogs and acclaimed black squid-ink rice.

A cluster of stylish contemporary hotels have recently blossomed to the south of the Herdade in Muda, joining trailblazer Sublime Comporta, with its bio-pool suites and interiors of Gervasoni furniture, polished concrete floors and white linen. September sees the opening of Independente – a mix of tasteful villas, laced through pine forest.

Another route to the Comporta good life is villa rental. Some are striking updates on classic Alentejo style, but they’re in high demand, so I head 18 miles south to the hills above Melides. Les Terrasses de Comporta, designed by Manuel Aires Mateus (a renowned Portuguese architect, shortlisted for the Mies van der Rohe Award) provides a startling 21st-century take on the region’s traditional aesthetic, with four linear concrete cabins crowning a forested ridge. Each has a faux façade, framing wide ocean views and creating a light, airy internal patio.

I set out for a final sunset drive towards the ocean, detouring along an unsealed track to pass the homes of the Cinzano empire heiress, a globe-trotting textile designer and, finally, Christian Louboutin, who recently opened his Vermelho Hotel in Melides village. As Comporta’s burgeoning fame and development takes its toll, is this the new discrete holiday frontline? Watch this (increasingly expensive) space.