Ainslie's eighth place in the final race of the Finn Gold Cup was enough to secure the title with a race to spare in Piraeus on Sunday.

Ainslie, 25, won Olympic gold at Sydney in 2000 to add to his silver in Atlanta four years earlier.

He then joined the One World America's Cup Challenge before leaving earlier this year to launch a third Olympic campaign, this time in the Finn, a larger single-handed dinghy.

After just over five months in the new boat, Ainslie also won gold at the European championships earlier in July.

"I can't quite believe that I have won this event, it is great," he said.

"I would never have imagined when I first started sailing the class earlier this year that I would have won both the Europeans and the Worlds.

"All of the British team has put a lot of effort into these two events and it seems to have paid off in the results."

Ainslie won the regatta by eighteen points from Poland's Mateusz Kusznierewicz and Greece's Emilios Papathanasiou.

His performance handed Great Britain a berth in the Finn class for the 2004 Olympic Games but Ainslie - the first British sailor to win the title since Chris Law in 1976 - will still have to qualify.

Defended

RYA Olympic manager Stephen Park said: "This can only be described as an awesome performance.

"Ben is clearly one of the world's best dinghy sailors, but nobody could have expected that after only five months in the boat he would have mastered the Finn in such a short length of time."

Fellow GBR sailor Andrew Simpson finished in ninth place overall, while team-mate Chris Brittle successfully defended the junior world championship title after finishing eleventh.

Ainslie will put his Finn campaign on hold to compete in Skandia Life Cowes Week, helming the Swan 70 'Volvo for Life'.

He will return to Athens to take part in the Olympic Test Event from 16-25 August.