Isle take it! Mediterranean islands are the super-rich's new must-have

It’s not just fresh supply that is boosting the market. Prices are falling, especially in Greece. ‘Some islands have lost 50 per cent of their value since 2007,’ says Christos Vergos, of the Athens branch of the property consultancy Remax.

The Mediterranean is the most prized location because it’s where the super-rich congregate. What’s the point of having bragging rights over an island if there’s no one around to brag to? But the Adriatic is growing in popularity, thanks to investments in new marinas, notably Porto Montenegro, and new resorts, such as hotelier Sol Kerzner’s first One&Only in Europe, also in Montenegro.

Closer to home, London’s property boom is helping to finance the purchase of new island realms. Eight hundred-acre Tanera Mòr, off the west coast of Scotland, comes with nine houses, three jetties, a café and post office, a workboat to cross the mile and a half to the mainland, and three freshwater lochs. The price is £2.5m. In Fulham that will buy you a family home.

The lure of islands is clear. ‘We all have a desire to rule our own domain and create our own playground,’ says Edward de Mallet Morgan of estate agents Knight Frank. Lord Glenconner started the trend when he bought Mustique 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 and David Bowie. London is now the centre of the private islands market. ‘We’re the global clearing house,’ says Weston Baker.

But it’s not all about bling. Savills recently sold an island off the coast of Finland for £200,000. Its USP? You can walk there in winter because the sea freezes over.

Buying an island may be seductive but it is tricky. There are all sorts of basic questions to resolve that even the super-rich never think of. The key one is: does the island have fresh water and electricity? The Turkish island market has never really taken off because most islands lack fresh water.

There are some big choices to be made. Uninhabited or inhabited? Choosing an uninhabited island, usually bought from investors or governments, means starting from scratch. The bills can be colossal.

‘You have to bring in water, electricity and irrigation,’ says Piers Williams, head of international sales at estate agents Aylesford International. ‘Either you make it self-sufficient and install solar panels and your own generators, or you bring in electricity through underwater cabling. Both require a large amount of expenditure. You need to have deep pockets and be a strong character.’

An inhabited island can include anything from a single house for the owner to multiple houses. Owners may have feudal-style rights over tenant farmers. Like a house, an island, uninhabited or inhabited, can be freehold or leasehold, depending on local laws. There are some nifty perks. If the island is outside territorial waters, the owner can declare himself or herself the ruler.

Buying an island takes time. It was four years before Al Thani could close the deal on his new Greek islands. ‘There’s a lot of paperwork to go through,’ says Ioannis Kassianos, Ithaca’s Greek-American mayor, with commendable understatement.

It can also get political. The Greek opposition is leading a campaign to stop the sale of islands. ‘We need to keep state ownership of all our assets — not sell them to the highest bidder,’ says Yiannis Milios, chief economist for the opposition Syriza party. ‘Experience shows that the privatisation of public goods is a very bad idea.’

Weston Baker disagrees. ‘The islands aren’t being bought and moved somewhere else. Their nationality does not change. They are there and they always will be there. New owners will bring new investment and new jobs, especially if the islands are formerly uninhabited. If new owners don’t invest, the islands just sit there, not generating much revenue.’

However much you might want to be king of all you survey, local rules mean the beaches may not be as private as you think. In the Mediterranean and much of the world, beaches up to ten metres above high-water mark are public property. Anyone can pop ashore.

But there are some who insist (mostly) splendid isolation is just splendid and have no desire to holiday any other way. Sir Richard Branson bought Necker, in the British Virgin Islands, in 1978 for an estimated £175,000. Not even a fire that destroyed most of his home in 2011 has tempted him to leave. He has just rebuilt his house and is carrying on.

David Copperfield, the illusionist, lets out houses on his island Musha Cay in the Bahamas and has even trained birds to pick up litter from his resort beaches. Sergey Brin, the co-founder of Google, got married there in 2007. If you have to Google it, you can’t afford it.