Iain Percy fears the price of failure as he stands on the verge of landing yet another sailing gold medal for Britain in Sydney.

Percy leads the Finn class by a mammoth 20-point margin and Friday's performance means he has still to finish outside the top 10 after an amazingly consistent regatta, unmatched in any other Olympic fleet.

The Southampton sailor will seal his place at the top of the podium if he finishes in the top four in either of Saturday's final two races or his nearest rival, Swedish world champion Fredrik Loof, finishes well down the fleet.

Britain's Shirley Robertson clinched victory in the Women's Europe Class by just two points and Ben Ainslie survived a protest by Robert Scheidt of Brazil to strike gold in the Open Laser class by just one point.

Percy, already assured of silver, said: "It looks good on paper but it won't be good enough if I don't get the gold medal.

"There is no celebrating now. I came for gold, not silver. It's a big lead and I would not forgive myself if I lost it.

"It's important I stay focused on the job in hand. The size of my lead does not really matter to me. I know what I need to do and I've only got one day to wait to see if I can do it."

Percy won Friday's ninth fleet race to increase his advantage over Loof, with Poland's Mateusz Kusznierewicz - the reigning Olympic champion - occupying the bronze medal slot.

After a day of high seas drama in Rushcutter's Bay, Britain are guaranteed another sailing medal on the final day of the regatta on Saturday.