Ineos Britannia scored their first America's Cup race win on Wednesday in their fifth outing as defenders Emirates Team New Zealand endured a disastrous start.
The Kiwis lead 4-1 after dominating the opening battles in the 37th America's Cup but Ben Ainslie's British team finally got off the mark after dealing with the light wind conditions better off the coast of Barcelona.
Ineos Britannia triumphed by one minute 18 seconds to stop the rot after four consecutive defeats.
Ainslie badly needed a victory to gain a foothold in the best-of-13 series which was slipping away from his team after they qualified for the race for the first time in 60 years.
"It's a good win for us, tricky on the start, we trained for those situations, we managed to make it stick and get them off the foil, it was pretty tough for them from then on," he said.
"There's nothing comfortable about sailing boats in these seascape, it's tricky, the guys did a nice job keeping the boat up on the foils... good one for the team."
In 2013, Ainslie produced a stunning comeback with Oracle Team USA against New Zealand, coming back from 8-1 down in a 17-race series to win -- and Ineos's victory on Wednesday sparked hope of potentially managing a similar feat.
The British boat nailed the pre-start while double defending champions New Zealand were late and fell off the foils in Ineos's dirty air, unable to get started.
Ineos opened up a lead of over 1.5 kilometres in the first leg, finding more wind in the top end of the course.
New Zealand were relying on a mistake from their opponents to have a chance of clawing their way back in, but it was not forthcoming.
"It's a bit of a shame we couldn't get across them and dropped off the foils," said New Zealand helmsman Peter Burling.
"It's obviously frustrating to be off the foils, we made a little error being a tiny bit too late but it was a bit unlucky.
"That's sport and I'm looking forward to the next one."
Britain hosted the inaugural America's Cup race in 1851 around the Isle of Wight but have never triumphed in the 173 years since.
Ineos Britannia, bankrolled by billionaire Jim Ratcliffe, the co-owner of Manchester United, are dreaming of lifting the world's oldest international sporting trophy for the first time.
The sixth race was scheduled to begin at 1315 GMT Wednesday.