But an island need not remain a distant dream. Financially it is more affordable than many people think. For about £800,000 White Island in the Grenadines could be yours. Shimmering sandy beaches, crystal blue waters, quivering palm trees — there’s even a mini craggy mountain. It could be the ideal location to play at Robinson Crusoe — or Swiss Family Robinson if your fantasy includes the kids.

But buying an undeveloped island requires a huge amount of work. White Island, which forms part of an archipelago south of Carriacou in the Caribbean, has no fresh water, no electricity and no house or dwelling of any kind. Getting there will mean chartering your own boat or aircraft from nearby Grenada. Unless you want to enjoy your private paradise from a hammock, tent or a palm-roofed hut, you will need to build a house.

All supplies and workforce must be transported to the island. As a rule of thumb, building costs will be 35 per cent higher than on the mainland.

The most important commodity on an island is water. In the absence of a freshwater river the options are digging a well, installing a desalination unit, collecting rainwater or shipping in supplies. Full-time island living requires about 100,000 gallons of water a year, so you need an annual rainfall of 40in or more to achieve that.

Nick Byrne, of Waterside Properties, says the reality of island-owning soon deters dreamers. Stunning pictures of White Island attracted lots of interest at this year’s Boat Show in Southampton, but no serious buyers. “Lots of responsibility comes with owning an island,” Byrne adds. “You can’t just leave it and hope everything is OK while you’re away. You need to make sure the house hasn’t suffered damage — say, from tropical storms — and you need to be careful of squatters. The utter privacy afforded by an island also raises security issues.”

While Waterside will arrange subsidised viewing trips to mainland properties, island-buyers will have to get there under their own steam. “That soon sorts the wheat from the chaff,” says Byrne, who is marketing White Island in conjunction with Vladi Private Islands, the foremost authority on island-buying. The island has been on the market for two years and is being sold on behalf of the Ferragamo fashion family.

Of the 800 or so privately owned islands recorded in Vladi’s Hamburg headquarters, about 30 are for sale. While White Island might be an untouched tropical paradise, Vladi is a big fan of the islands dotted around Canada’s coastline. “If you can swap palm trees for spruce, British Columbia is fantastic. In the Caribbean and Bahamas the weather is a problem. In Canada there are no hurricanes.

For four to five months of the year the weather is excellent — you wouldn’t want it to be warmer. You can buy a Canadian island for around £100,000, which would give you as much enjoyment as one in the Bahamas costing ten times that amount.” ()

The demand for islands has risen as transport and technology developments make self-sufficiency more attainable. Vladi believes, however, that it has encouraged charlatans to enter the market. In particular, Vladi says islands in the Philippines and elsewhere in Asia are being offered illegally. It is vitally important that prospective buyers do their homework and employ an independent local lawyer — wherever they are thinking of buying, but especially in distant locations far from the mainland.

Closer to home and legally available are the many islands dotting the dramatic Norwegian fjords and vast Finnish lakes. The Greek, Croatian and Italian coasts also offer a smattering of sought-after Mediterranean jewels.

A beautiful island off the coast of Brittany has just come onto the market. Gravinis, in the Golfe de Morbihan, is one of about 30 or so islands mostly owned by French film stars and other Gallic heroes. The 35-acre (14-hectare) island has fields, woods, its own megalithic monuments, two big houses and offers access to the ocean as well as the protected waters of the gulf. All this is available for €3.5 million (£2.4 million), barely enough to buy a half-decent château on the mainland.

If deciding on a particular ocean or archipelago is proving hard, consider renting an island for the summer. For €10 Vladi will send you a glossy catalogue of dozens of palm-fringed islands for rent. Perfect fuel for winter dreaming.

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