Big skies, pale quartz beaches, cottages selling designer brands ... Claire Wrathall is captivated by Germany's alluring Friesian Islands

Five years ago, the German television channel RTL commissioned a pilot for a home-grown version of Fawlty Towers. Basil and Sybil became Viktor and Helga, who presided over a chaotically awful hotel called Zum letzten Kliff. But just as the Manuel character - reinvented as a Russian waiter called Igor - bore little relation to his Barcelona-born original, so its setting, the holiday island of Sylt, was a far cry from Torquay.

Just off Germany's Jutland coast, on the same latitude as Newcastle, Sylt (pronounced "zoolt") is the largest of the North Friesian Islands, an unexpectedly alluring archipelago with a microclimate that ensures the North Sea here is far warmer in summer than it ought to be. It laps (or lashes, depending on the wind) a 35km stretch of pale quartz sand, the loveliness of which has caused the island to become the German élite's holiday haunt of choice, a sort of Teutonic Hamptons - like Long Island it is long, narrow and flat, the big sky punctured only by the odd lighthouse. Both places have a whaling heritage and miles of beach, and both are dotted with settlements of fabulous houses. Sylt may have a population of just 21,000 and an area of less than 39 square miles, but it has three Michelin-rosetted restaurants, and Kampen, its most exclusive village (home to a mere 600), has branches of Bulgari, Cartier, Chopard, Christoflé, Escada, Hermès, Joop, Louis Vuitton, Swarovski, Tod's and Wempe, each in its own thatched cottage. Inevitably it's not a place to court trippers, and does its best to be inaccessible. There are ferries only from Denmark, and even though it's connected to the German mainland by a causeway built in 1927 to bring the railway, there is no road access. If you want to bring a car - and lots do if you count the Porsches, BMWs and Mercedes (almost the only imports are Aston Martins and Maseratis) - you have to put it on the train at Niebüll. Next month, however, the German low-cost carrier Air Berlin launches a route from Stansted to Sylt, which should raise the number of foreign visitors. For during the week we spent there, we encountered only one other Brit, and she was married to a German. Our presence as foreigners on the train from Hamburg was reckoned to be so unusual that another passenger approached us to check we were on the right line. How did we know about Sylt? he asked. It was very unusual for Ausländer to be going there. He'd been holidaying there for 25 years and had hardly ever seen one, but he was generous with his advice on what to do and where to eat.

Arriving by air, you'll land in the island capital Westerland, which is as close as the Friesian Islands come to a mass-market resort. But its splendid beach apart, it is a lot less attractive than the rest of the island. Better to base yourself on the east coast, in the village of Keitum, say, an almost surreally pretty place of story-book cottages with thatched roofs, roses round the door and carefully tousled country gardens shaded by chestnut trees that make you think of England. Until you realise, of course, that the quintessentially English thatched cottages were not originally English at all. They were brought by the Jutes from Jutland.

The only downside to this side of the island is that there is no real beach. The east of the island looks across a nature reserve known as the Wattenmeer, mudflats that are paradise for birdwatchers and lovers of shifting, watery, richly coloured vistas, all blues, browns and silvery light. A landscape of such resonant beauty that it has inspired its own verb: Wattwanderungen, to walk the Watt. Though in many ways, cycling is a more practical way to cover the island, especially if you want to get as far as Hörnum, another picture-postcard settlement with a striped lighthouse, on the southern tip.

This is the departure point for ferries to the other North Friesian islands, notably Amrum and Föhr. These are altogether less developed and less expensive than Sylt. But Föhr, in particular, is an enchanting if sleepy place. Amrum (pop. 2,400) is sleepier still.

The distances between the islands look negligible on a map; indeed at low tide it's sometimes possible to walk between them, though you must go with a guide to avoid quicksand, marked on the map with skulls. Ships have to take account of shallows and sandbanks, so the passage from Sylt to Föhr takes a slow two hours, a trip that took us not just across the water but apparently back in time to the bucket-and-spade holidays of my childhood. For though it has a splendid sandy beach with a proper promenade lined with cafés (the nicest is Valentino), the principal resort, Wyk, has nothing in the way of amusement arcades or fast-food outlets, and by 9pm the place is dead. If you're looking for entertainment beyond building sandcastles and basking in the shallow water, then practically all that's on offer is bedtime-story-telling by the town bandstand - a nod to the fact that Hans Christian Andersen holidayed here in 1844.

Our hotel, the serviceable but rather charmless Schloss am Meer, lent us bikes so we could explore the island. Even flatter than Sylt and largely given over to pasture - this is the home of Friesian cows after all - it is reminiscent of East Anglia, its great green interior cross-hatched by a grid of dykes dating back to the Middle Ages. This enduring landscape remains as it was in 1903, when it was evocatively described in Erskine Childers' ripping and prescient 1903 thriller The Riddle of the Sands: "A low line of sandhills, pink and fawn in the setting sun, at one end of them a little white village huddled round the base of a massive four-square lighthouse - such was the easternmost of the Frisian Islands, as I saw it ... In faint outline was the flat plain of Friesland, broken only by some trees, a windmill or two, and a church spire. Between, the shallow expanse of sea was already beginning to shrink away into lagoons."

On Föhr, there are 17 villages of almost improbable prettiness, and though Nieblum is the most celebrated, I'd say less touristy Oevenum is arguably lovelier. Just as I think Föhr may slightly have the edge on Sylt. It may not have the style and sophistication of its neighbour, and it definitely lacks its excellent hotels and restaurants (though we liked Alt Wyk, a traditional merchant's house on Grosse Strasse, where we dined on a salad of cheese and samphire, slip soles and spinach) and wished we'd been staying. But as a retreat from the pressures of life, as respite from the modern world, it's a sweet, quite touchingly retro place. Somewhere with a real sense of the recent past, where there's quite likely a hotel that's just like Fawlty Towers.

Air Berlin (0870-738 8880; flies from Stansted to Sylt from 2 May. For ferry details, contact Adler-Schiffe (00 49 4651 98700; Hotel Schloss am Meer (00 49 4681 58670; hotel-schloss- Alt Wyk (00 49 4681 3212;