After two days of worry, Sir Ben Ainslie and Land Rover BAR effectively booked their place in the Louis Vuitton America’s Cup Challenger play-off semi-finals as the introduction of Jono Macbeth, a three-times America’s Cup winner, helped them to a commanding victory over Artemis Racing on the Great Sound yesterday.

BAR had lost four successive races since beating Artemis in their opening match on Saturday, as they had started to look worryingly off the pace. But after a devastating defeat by Groupama Team France on Monday, an evening of soul-searching and the introduction of Macbeth for the first time resulted in them sailing a near-perfect race to beat the Swedish team by 30 seconds.

Only an incredible sequence of results could prevent BAR from reaching the play-offs, which begin on Sunday. Their place could be assured before they next race against Emirates Team New Zealand today, if SoftBank Team Japan beat France in the day’s first race.

The presence of Macbeth at grinder helped to settle the team, according to Ainslie. “Jono has that experience and has that presence,” Ainslie said of the 44-year-old. “If the guys on the other boats look across and see him there, it will probably put the shivers down them a little bit.

“That helped to settle the boat today and that’s what you need, to bring on some big-name players and put on a performance.

“It was a huge setback for us, losing to France. For the team, it was a really tough moment and we had to go back and had a lot of debriefing about how we sailed and the set-up and performance of the boat to get the speed we need. That’s why I am really proud of the team. We have not had the perfect build-up to this competition, by any means. The way the team responded is absolutely remarkable; we are a strong team.”

For the fourth race in a row, Ainslie won the duel at the start and BAR hit 43 knots as they built a lead in the run to the first gate. Thereafter, the British team sailed a solid race, holding a steady lead throughout. Only once, as they tacked at the fourth gate, did they make any semblance of a mistake, coming down off their foils, but unlike errors in previous races that proved terminal, this time they recovered their speed quickly.

It was the second time they had beaten Artemis, having come out on top when they met in similar conditions over the weekend.

“It seems to be a sweet spot for us, light to medium breeze,” Ainslie said. “The trick is taking ourselves up the wind range. Yesterday, we struggled a lot against France with the configuration we had.

“We went back to the drawing board last night about how we could get the speed and the controllability of the boat, as we know that’s the challenge. It was a great win because, as you know, we’ve been on the back foot. It has been hard for the team and it was good to turn that around.”

David Carr, the grinder, said the presence of Macbeth made a big difference.

“I’ve been with the team for four years and last night was about as low as I can remember,” Carr said. “The bloke’s done like 20 America’s Cup matches. You cannot buy that experience.

“He’s still a strong old beast; that’s why we call him ‘The Bear’. But his temperament blew me away. He brought an attitude on to the boat that resonated across the crew. He is the sailing team manager and he locked us down. He has the finger on the pulse of our group.

“I think that’s as clean as we’ve ever sailed. For us to sail fast, we are asking a lot of Ben and CJ [Paul Campbell-James, the wing trimmer] at the back. We have a very small window. But they were perfect today.”

With the pressure about reaching the semi-finals now lifted, BAR have a busy day today, facing both New Zealand and France, in lighter winds, with the breeze possible so light that it could threaten racing altogether.

“It is going to be close [to the lower wind limit],” Ainslie said. “It will be interesting to see how the teams perform down the range and how those light-air foils are performing.

“Some of the teams are more consistent over a range of conditions; that’s what we have to work at.”