Ben Ainslie will attempt to clinch his second successive Olympics sailing gold medal on Saturday after sealing at least a silver in the Finn class.
The 27-year-old, who has won silver and gold in the Laser in the last two Games, is in pole position after his fourth win in 10 races in Athens.
Ainslie holds a 14-point lead over second-placed Spaniard Rafael Trujillo.
Nick Rogers and Joe Glanfield are also assured of at least silver in the men's 470 ahead of Saturday's final race.
The British pair led by 10 points after a 10th place in Thursday's first race, but a disappointing 19th in race 10 leaves them trailing Americans Paul Foerster and Kevin Burnham by two points.
"We are really pleased to have the silver," Rogers said.
"If Paul (Foerster) tries to take us out to the back of the fleet, then at least we have already got a medal.
"We didn't sail that well today but are going to come out all guns blazing on Saturday and take them on for gold."
The pair are 24 points ahead of third-placed Sweden, so cannot be overtaken for silver.
"It really will be gloves off for the gold medal," Glanfield added. "They are going to come at us hard."
Ainslie cemented his dominance of the Finn class with a second in Thursday's first race, his sixth top-three finish in nine.
He then led from start to finish in race 10, but remains cautious ahead of the final race on Saturday.
Glanfield (left) and Rogers will fight for gold
"I've got one race to go with a nice cushion on the Spanish guy but it's not
over yet - he's still lingering," Ainslie said.
"I still have to go out there, concentrate, focus and try to stay near him
and if I'm within 14 places that should be enough.
"But I was delighted to nail home two really good races today.
"I was a little bit tense going out because it was still very close overall and the wind was pretty light. It's always tricky when its like that."
Meanwhile, Paul Goodison is only a point outside the medals in fourth place in the Laser after winning race seven on Thursday.
Greece's Sofia Bekatorou and Aimilia Tsoulfa won the first gold medal of the regatta
after taking an unassailable lead in the women's 470 class.
The four-time world champions, only 14th in Sydney four years ago, triumphed with a race to spare having dominated throughout the competition.
British pair Christina Bassadone and Katherine Hopson have an outside chance of a medal after finishing second in race nine and 17th in race 10, leaving them seventh overall.