The well travelled and well-heeled are deserting the crowded playgrounds of St. Tropez and Monaco. Instead they are searching out places that offer the greatest modern luxury of all – privacy. A decade ago the fashionable way to ensure holiday solitude was to purchase a château where you could, quite literally, pull up the drawbridge and keep the world at bay. But now the solution for the discerning and financially well-endowed holiday-maker is to buy a private Island.

`Private Islands are purchased by the ultra-wealthy and famous for security, Investment and privacy - but mainly to live a dream,' says Steve Donovan of Damianos Sothebys International Realty, a private Island specialist. `Everyone has a place in the back of their mind where they live an a beautiful and deserted tropical Island.'

The bad news is that while demand for private Islands has undoubtedly increased, with celebrities including Johnny Depp and Diana Ross joining the Clique, supply hasn't. There simply aren't enough new Islands coming up for sale.

The Island market is very similar to that of oil paintings,' says Farhad Vladi, owner and manager of Vladi Private Islands, who currently has 126 freehold Islands for sale an bis books. 'You only have a few quality Islands that come an to the market sporadically. The really good islands are normally not to be found an any websites or in brochures. They are mainly sold privately.'

So what is the secret to finding the perfect Island hideaway? As rising demand has shrunk the available supply, the first step is to be flexible. If you can't find the perfect, fully developed Island, you should consider doing a Spot of DIY.

Turning a deserted Island into a luxury retreat isn't as hard as you might think. In fact, the latest building techniques have had a significant Impact an the Island market. A prefabricated home, electricity and water (drill or desalination) can all be made available within three months. This greatly increases the available stock.

Next you need to focus on the right areas. No matter how substantial your funds, you can't purchase an Island anywhere you fancy - whatever some unscrupulous agents might suggest. In some of the more exotic and desirable areas, foreigners are simply not allowed to buy freehold properties.

`New markets will only come up if laws change - such as in the Philippines or in Indonesia - and foreigners are permitted to purchase there,' says Farhad. In fact, the South Pacific (specifically Fiji and French Polynesia) and the Caribbean are two of the few exotic areas where foreign purchasers are welcome.

Legal restrictions are one reason why the private island concept has evolved beyond tropical paradises. Now unspoilt sanctuaries in colder climes are beginning to enter the market. Keholmen on the west coast of Sweden is a perfect example. A 12-acre island with two houses, workshops and a sauna on the seafront - well, it is Scandinavia - it's for sale through Vladi Private Islands for 1.725 million. A new boat is included in the price.

However, if you must have sun with your sand, then the number one private island hotspot is undoubtedly the Bahamas. This is a highly competitive market, so it's worth looking at undeveloped properties. White Bay Cay, for example, is a spectacular 3o-acre freehold private island in the heart of Exumas Cay, with a price tag of $7.5 million. lt lies between several protected islands in a land and sea park 6o miles southeast of the capital, Nassau. The island possesses good elevations for building sites and deep-water access, with a natural area for a small harbour. It is for sale through Damianos Sothebys International Realty.

However, before you kick off your Gucci loafers and walk barefoot on the beach, it's important to get expert advice. A good agent will do a thorough investigation to ensure that ownership is clearly established and officially recorded. They will research local laws regarding building regulations and fishing rights, as well as looking at practical details such as spaces for parking (boats and cars), proximity of the nearest hospital (no more than qo minutes away), sanitation and energy.

'The two big pitfalls for potential buyers would be working with unscrupulous land sellers and not doing due diligence on the property,' says Steve. `These are avoidable by working with professionally licensed real-estate agents and approaching a property with both eyes wide open.'

Wherever you buy, your overall budget should take into account any extra costs - legal charges are likely to be higher than with a simple property purchase. If you want 'frills' - your own private sheltered harbour equipped with jetty for the yacht, a helipad or airstrip - your dream is going to cost you a whole lot more. But the rewards speak for themselves.

An island that has been carefully and lovingly developed often feels like part of the fan-iily,' says Farhad, who proves to be surprisingly poetic for an estate agent. 'It is said that an island does not have a house number; an island has a soul.'