$325m to sail away in the lap of luxury

The Platinum, also known as the Golden Star, is longer than a naval destroyer, and carries its own submarine.

It is the ultimate in conspicuous consumption, the biggest yacht in the world.

The Platinum, being built in the Middle East, is the size of a small cruise ship. It is longer than a navy destroyer and drips with luxury beyond most people's wildest fantasies.

The yacht's details are swathed in secrecy, but Britain's Sunday Telegraph has discovered that the sleek 160m vessel, also known as Golden Star, will boast the latest must-have accessory for owners of "super-yachts" - its own submarine.

The Platinum's owners will also be able to use a helipad, a hangar for small aircraft, and garages for jet-skis and four-wheel-drive vehicles, which can be taken ashore on landing craft.

Inside, they and up to 24 guests will enjoy a stylish interior design and gaze at original works of art.

A health spa offering every conceivable health and beauty treatment will complete the pampering.

Doctors and nurses will be on duty, and electronic security and sophisticated weapons will be installed to deter any unwanted callers.

The cost of the sumptuous project is being kept secret but is estimated at more than $325 million.

The man paying for it is Sheikh Mohammed bin Rashid al-Maktoum, the Crown Prince of Dubai.

The super-yacht - or megayacht, as such giant vessels are called - is under construction in the United Arab Emirates and is expected to be completed next year.

It will be comfortably bigger than the reigning giant of the yachting world, the lavishly appointed 137m Rising Sun, owned by Larry Ellison, the chief executive of the Oracle software company.

The Platinum was commissioned in 1996 by Prince Jefri Bolkiah, the younger brother of the Sultan of Brunei, the world's richest man.

It was being built by two German companies, Lurssen and Blohm and Voss, but Prince Jefri ran into financial difficulties and the project was suspended in 1998.

The unfinished yacht remained at the shipyard until 2001 when Sheikh Mohammed arranged for it to be moved to the United Arab Emirates, where construction resumed.

The world has 800 motorised and sail super-yachts - generally defined as those more than 30m long - but more than 200 others are due to be finished in the next three years.

Super-yachts have grown from an average 30m to more than 45m in the past 10 years, and the market has tripled since 1997.

As ownership increases, builders say, a yacht has to be getting on for 60m to make the owner feel special. And Yachts International says at least 35 yachts are being built on that scale, including five which will be around 90m. Norberto Ferretti, chairman of the Ferretti Group, one of the world's biggest yacht builders, said super-yachts brought exclusivity, privacy and freedom. "Entertaining guests on a yacht is much more special than just bringing them to your villa," he said.

"Rich people can go to a beautiful hotel and pay US$3000 ($4190) a night for a suite.

"The trouble is that when you go down the lift, you're in the lobby with people who paid 20 times less. My clients don't like that."