by Malcolm Prior BBC News Online

The windsurfers are blown by 27 turbines across the pool

But now the traditional hallmarks of the popular watersport have been replaced by wind turbines, a swimming pool and a launch ramp at the UK's first indoor championships.

At a cost estimated to be about �650,000, organisers of the London Boat Show event have brought the great outdoors, indoors.

In a huge tent with a 1,700-seating capacity, 27 two-metre-wide turbines blow out gusts of wind reaching 30 knots.

The windsurfers are launched from a specially-designed ramp onto the 70-metre by 30-metre pool where they take part in a host of events, including freestyle tricks, jumps and even slalom 'duels'.

On Sunday, the winners of the UK heats will take on seven of the best windsurfers from around the world, a line-up which promoters claim proves the attraction of the indoor move for both competitors and spectators.

The windsurfers are blown by 27 turbines across the pool

One of the event's judges Fred Willis, who also helped to organise the championships, told BBC News Online: "When it's good for the windsurfers it's windy as hell on the beach, which is not that great for spectators.

"By bringing it indoors, you can see the whole thing and show the public what it's all about."

One of those trying out the new sport is Andy King, from Sholing, Southampton, who is competing in the freestyle and jump events.

And an added attraction for the spectators - and a test for the judges - is the fact that the 27-year-old will be competing in the same events as his twin brother, Steve.

He said: "Some people do see that as a novelty.

If you look upwind here all you can see is a turbine Andy King, Southampton windsurfer

"Before, when we used the same equipment, the judges were getting confused so we decided to change equipment but they still confuse us outside of the competition.

"It's all good fun and gives us someone to train with."

Andy, a second-placed contender in the 2003 British Wave Championships, believes that moving windsurfing indoors will catch on, despite the challenges it presents.

He said: "It's a lot more difficult because normally when you are windsurfing, if the winds are gusty, you can see them coming by looking upwind, but if you look upwind here all you can see is a turbine.

"But we are gradually getting used to it. It's a novel experience and a great spectacle for people to see."

Indoor revival

While the championship is the first in the UK, the sport began 14 years ago in Paris' Bercy stadium.

Organisers say the London event is the beginning of a revival that will see another event in Paris in March and plans to set up a European circuit.

But, at such a huge cost and with difficult conditions on the water, will indoor windsurfing become the new craze?

Despite the interest it has generated, Mr Willis believes it will remain for serious competitors only.

He said: "Indoor windsurfing is for the best only, because it's extremely difficult.

"Although the wind is coming out at 30 knots on one side it dissipates very rapidly.

"It's a very, very gusty and violent wind. It's extremely difficult to sail on it.