LET'S be clear: this is not any old beach. That's obvious when my two-year-old son and I stop, bemused, to watch a pretty Portuguese woman disappearing by inches under the almost impossibly golden sand as her giggling friend buries her up to the neck.

Apparently, they're testing its therapeutic qualities - it's said, with some scientific backing, that each grain, born of volcanic origins, contains a magical mix of minerals just bursting to cure a raft of bone and skin ailments on human contact.

Though it feels silky soft underfoot, I can't swear to any medical benefits. But I can tell you that this 5.5 mile (9km) swath of undeveloped beach - not a sun lounger, Coke bottle or beach peddler in sight - works its own magic for toddlers.

As every family who hotfoots it to the West Country knows, a good beach is all you need to keep the very young happy. But for everyone fed up schlepping down the A303, this one is worth running the gauntlet of Gatwick.

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There's more sun than Cornwall - temperatures in the twenties tempered by an Atlantic breeze, and, crucially, there's no time difference from the UK. What's more, from last week, it became a three-and-a-half-hour hop away, with the introduction of a new charter to Porto Santo.

To where? To Madeira's tiny neighbour, 27 miles to the northeast. Discovered in the early 15th century by the Portuguese, who still flock here with their families in the summer, the island is otherwise largely unknown because previously access was only by ferry or expensive local air service from Madeira.

Where mother nature smiled on Madeira, endowing it with green, fecund peaks, there was little left over for the lower-lying, arid Porto Santo, apart from the one thing Madeira lacks - a magnificent beach.

“We come here often for a great beach holiday, but I wouldn't say that there was anything else here to do,” says Robin Stickells, a South African visiting from his Madeira home with his three young children.

He's right - my son, Christian and I, find little to distract us from the beach on this island that can be circumnavigated in a car in 30 minutes, its northern side a moonscape of grey, sheer rock faces, out of which rises an extinct volcano once topped by a castle to fight off pirates. A plethora of new homes, a handful of old windmills, one of which has been turned into a café, and a criss-cross of dusty walking trails with a few springs where the soft, tangy mineral water is said to have similar qualities as the sand, and that's it.

Apart from Christopher Columbus, that is, who married the governor's daughter, Filipa Moniz, and lived with her for a time in Vila Baleira, in a house that is now a museum.

We enjoy a pleasant amble around the sleepy town of white, tiled buildings interspersed with palm trees, which is conveniently located a comfortable stroll from our hotel, the Pestana, at one end of the beach. At the other end, we stop at O Calhetas, where we feast on the local speciality of scabbard fish in a passionfruit sauce topped with a banana.

The beach turns out to be a bit of a walking track to food, backed as it is by half a dozen eateries, including my favourite, Pe na Agua, a seaside shack renowned for its caiparinias.

A handful of hotels, too, are strung along the sand, and like the march of the dunes, they keep coming. The Pestana, a pleasant, sleepy resort that opened its alarmingly coloured burnt sienna and yellow ochre buildings in April, is the first of a new wave. Behind the dunes, several cranes and half-finished buildings loom and you almost feel you're in a mini-Dubai.

It's plain the beach won't stay this quiet and idyllic for long. Nor will the secrets of its sand remain unlocked - the Porto Santo hotel is opening a spa featuring sand treatments at the end of the summer. Until then, you'll just have to do what I did - get your toddler to sprinkle fistfuls of sand all over your legs.

NEED TO KNOW

Seven nights at the five-star Hotel Pestana Porto Santo with Holiday Options (0844 4770452, www.holidayoptions.co.uk ) costs from £499pp (and £299 per child), including flights from Gatwick, transfers, and B&B

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