Situated about 18 kilometres offshore from Hoi An - the charming, yet ever- so-slightly sanitised, ancient port that doubles as the country's most foreign-friendly enclave - the archipelago is hardly an obscure outpost. When Hoi An was the commercial capital of the Champa kingdom, which ruled central and south central Vietnam from about the seventh century to 1832 and controlled the spice trade between Indonesia and China, the leeward anchorages on the western side of mountainous Hon Lao, the archipelago's main island, provided shelter for vessels from the northeast monsoon.

The island remained an important stop on the trading route even after the Viet people superseded the Cham and its hitherto rich fishing grounds pro- vided a decent living for its inhabitants.

Cu Lao Cham has, therefore, been on the radar for millennia and should, you'd have thought, be a prime target for the development frenzy enveloping this corner of Indochina. However, with accommodation on Hon Lao restricted to four simple guesthouses, basic homestays in the villages of Bai Lang and Bai Huong, and camping on the gorgeous tourist beach of Bai Chong, favoured by the handful of companies operating excursions to the island, it is clear that this won't be the next Phuket anytime soon.

There are a couple of reasons for this. The most prosaic is the weather. The winter monsoon hits central Vietnam particularly hard and conditions are generally pretty dismal between October and January. Shallow water levels at the entrance to the Thu Bon River make it almost impossible to visit the islands during this period and they remain only sporadically accessible until April.

The other deterrent to visitors is that Cu Lao Cham has been controlled by the Vietnamese military since reunification in 1975 and was largely off-limits to visitors until the early part of last decade. Nobody seems sure why access was so restricted, but the most prevalent theory is that a lucrative trade in the birds' nests hidden high on the cliffs on the eastern side of Hon Lao had something to do with it. Even today, access to the east part of the island is strongly discouraged by the military while opportunities to explore the verdant interior are conspicuous by their absence.

Many observers in the local tourism industry believe this isolation has been more of a blessing than a curse for the Cu Lao Cham islands.

Lodovico Ruggeri, the Italian who runs the Cham Island Diving Centre - established in 2002, it was one of the first operators to run excursions to the archipelago - is of the opinion that the military presence has acted as an effective brake on development.

'As long as the army is on the island it will remain relatively unspoiled,' he says over icy La Rue beers at his company's base, in the centre of Hoi An. 'The potential of Hon Lao has not gone unnoticed among developers. Hon Lao has got some of the best beaches and most pristine waters in the region. How could it not be on the radar?

'We've witnessed a huge rise in demand for the island in recent years and that's not going to slow, but the fact that the military is so protective of its territory means that the construc- tion boom being seen on the mainland is unthinkable.'

The same thing was no doubt once said about other island favourites in this part of the world, but it's hard to picture Hon Lao as a mainstream resort destination.

As our group descends into Bai Lang after a trek along the single potholed streak of tarmac that acts as the island's main highway, a languid rhythm of life becomes evident. Tiny silver fish catch the sun as they are laid out in the streets to cure; groups of teenagers hide in the shade around plastic tables on pavements, smoking cigarettes and drinking ca phe sua da (iced coffee with condensed milk); and every second garden seems to be occupied by shirtless elderly men napping in hammocks.

It's a romantic scene and one of those that cash-rich and time-poor tourists tend to idealise. Life on the island, however, is far from a bed of roses. Overfishing both by locals and out- siders from as far away as China and Japan has severely depleted stocks and local youngsters are more attracted by the bright lights of the cities than they are by the simple life on Hon Lao.

'They go and they don't come back,' our boatman, Viet, himself an islander, says ruefully.

On the boat back to the mainland, Beth, an Australian tourist who spent last night sleeping on Bai Chong with her friend, says, 'It was perfect. Just us, a few bottles of beer and the stars.'

Hon Lao may not always be so idyllic, but, for now, it is a choice refuge from the rat race.