No man is an island...

Thanks to low-cost airlines, almost anyone can now gain access to remote or once-exclusive places, and the sheer number of people competing to share the same few precious grains of sand is reason enough for celebs and the super-rich to invest in a private island of their own.

Plenty of private islands are there to be had, but it's all a question of price. The 110-acre Rang Yai Island near Phuket is currently on the market for £100 million; the 2,000-acre Ronde Island in the Caribbean for £62 million. Of course, demand is fuelled by supply. Last year, 150 islands from Croatia to Brazil were bought by rich Italians. The higher the budget, the more exotic the location (just 250,000 buys you a bolthole in Northern Europe, the Canadian lakes or Croatia).

'The wealthy look at more exotic places, such as Central America,' says Mario Breglia of the Milan-based Scenari Immobiliari property research group. Their justification for such self-indulgence is that they are saving the planet by keeping such a large chunk of it for themselves (and not building tacky high-rises on it).

Famous island owners include Johnny Depp, who bought Little Hall's Pond Cay in the Bahamas in 2004 for a bargain $3.6 million; Brad Pitt and Angelina Jolie, who allegedly bought a 4km island in 2007 in 'The World', Dubai's offshore man-made archipelago, for $10 million; and Richard Branson, who bought Necker Island in the British Virgin Islands for $200,000 in 1979. Others include Mel Gibson (Fiji), Julia Roberts (Bahamas) and Nicolas Cage (also Bahamas, where your own sandy fortress will set you back £7 million). Of course, celebrities hate to be in any place where there aren't other celebrities so they buy islands right next to each other so they can jump in their speedboats and drop by for dinner. In fact, it can be so lonely living on your own island that the new trend is to buy one giant island and get all your friends to build houses there, too.

Seeking privacy from the hoi polloi is hardly new. The principle behind Mustique was for the super-wealthy not to have their holiday polluted by anyone not exactly like themselves. Lord Glenconner bought the island in the 1950s and it attracted Royals such as Princess Margaret (who was given a plot of land by Lord Glenconner as a wedding present) and celebrities, including Mick Jagger, David Bowie and Pierce Brosnan. Of course it did: private islands where you can't buy property without passing a vigorous vetting process are essentially gated communities, exclusive ghettos of which ordinary mortals will never get so much as a sneaky peek.

This is the idea behind the new resort of Meganisi, a Greek island, 7km of which (roughly half) is being developed for private ownership by Lord Jacob Rothschild, using London's Studio Seilern Architects. The island is a 40-minute flight from Athens, but according to architect Ivan Lazzaroni, most residents will helicopter in. Anish Kapoor is said to be one of the interested parties. There are 15 plots for sale, with private or shared beaches, ranging from four to 40 hectares, along with a marina village and two hotels. But the big idea, says Lazzaroni, is that only a select group (ie, the owner's friends) will be invited to buy.

If you can't afford your own island, it's worth cultivating friends who can. Designer David Bentheim, presently finishing a house for a wealthy family on a private island in the US, says, 'The best thing about private islands is there are no arguments, and no traffic jams on your way to and from the beach. It's also very unlikely you'll bump into anyone you don't know or that you hate.' Bentheim once stayed on a private island belonging to friends in the Bahamas. 'When we went out for lunch, if we saw another boat, we'd go to another island. The most frightening thing was being dropped off on an empty island with a picnic for lunch by the staff. We were terrified they might not come back.'

Which is a worry that hints at the less glamorous side of island life: not all locals are necessarily appreciative of the philanthropic, green efforts of the new owners, or their extreme need for privacy, and unstable, changing local governments make buying an island a high-risk proposition in many cases. The more remote, the more difficult, and sometimes dangerous. As Bentheim says: 'Everything is gorgeous on these private islands - until they machete you to death.' ES