"We're all friendly rivals," says Ainslie. "All the boats competing in the America's Cup are based here and it's a small island, so we socialised together when we first arrived, but as the race has got closer, things have become more competitive. We don't go in for friendly barbecues any more."
The sailors have gone from regarding one another with casual, eclectic curiosity, to scrutinising one another like hawks.
"I love that. I love the daily, hour-by-hour competitiveness of it," says Ainslie. "We're up against France, Sweden, America, Japan and New Zealand and we're all different; but we all want to win."
Ainslie's team, Land Rover BAR (Ben Ainslie Racing) is a serious contender, with 120 employed on the campaign, half in Portsmouth analysing data, and half in Bermuda. You can't help thinking that those based in England must be a bit peeved. Bermuda is beautiful: with its arresting pastel- coloured houses dotted through the trees and the sea teeming with gun-metal grey boats.
For Ainslie this race is hugely important: his name is on the boat and he is staking his reputation on his ability to bring the Cup to Britain.
"There's a lot of responsibility but I think this team can do it. The trouble is that it's very hard to do it on your first attempt," he says. "Only once in history has a new team won the race, we're in it for the long haul and I do believe we will win."
As Ainslie speaks he is overflowing with enthusiasm and warmth for the task ahead. I wonder whether he realises that, despite all his warnings about how difficult it will be, everyone is expecting him to win. He is the most decorated sailor in Olympic history and when he delved into America's Cup racing before and took over as tactician on Oracle Team USA, he transformed the boat's fortunes. They went from 8-1 down to winning 9-8. It was the biggest turnaround in sporting history.
"I appreciate that there's expectation,' he says. 'And I don't want to let anyone down."
Winning for the Americans will be nothing compared with winning for Britain, if he can pull it off. This is the only sporting trophy this country has never won and it has been around since 1851.
He started putting together a campaign strategy in 2012, but it wasn't until the end of 2013 that he made the decision to go for it - initially relying on funding from Charles Dunston and Keith Mills, sailing enthusiasts and friends, before Land Rover arrived in 2015 and transformed everything.
"That was the turning point,' he says. 'That's when I knew we could have a really good stab at winning because they brought money and expertise."
America's Cup sailing is very different from the Olympic sailing in which Ainslie made his name. He describes it as being like Formula One on water.
"It's high speed and exhilarating. When these boats turn a corner the g-force is serious. If someone makes a mistake around a marker, you don't have a chance of staying on. I feel like a racing car driver or a pilot, it's that sort of intensity."
Since only two per cent of the boat's mass is in the water when they are up on foils, it is more like flying than sailing and much faster than any previous boats - yachts competing in the 2007 America's Cup had a top speed of 12mph, today it's closer to 60mph.
It is also more dangerous than traditional sailing. Ben is 40 now, married, to Georgie Thompson the former Sky Sports presenter and with a young daughter, Bellatrix. He lost his great friend Andrew 'Bart' Simpson in an accident while Simpson was training for the 2013 America's Cup, so does safety worry him?
"I'm not as bullish as I used to be and we're all more focused on safety than ever before, since Bart, but I feel safe, so to a certain extent you've got to get on with it."
From the outside, the sport is remarkable to witness. The boat flies through the water while sailors scurry across the top of it, moving like they are in some exquisitely choreographed ballet.
If one of them moves too soon or to the wrong place, the boat won't do what Ainslie is trying to make it do. "No one can put a foot wrong," he says. "Or we lose."
It's like trying to perform tasks on a car roof while it roars along a motorway. In preparation, the crew have been mentally challenging themselves while engaged in exercise, chess on a treadmill; scrabble on a bike? "That sort of thing," says Ainslie. But mainly they have been training on the water for up to six hours a day.
Ainslie has had to lose weight for the race in order that others on the boat, who do the more physical tasks can be bigger, so they share out the weight allowance. When he was sailing in the Olympics, he weighed about 15st, now he is under 13st.
"I'm on a constant diet. We haven't got to the point where the big guys are buying kilos off me, but that time may come."
There's a rather lovely moment when I go for dinner with members of the team that night and find myself sitting beside Leigh McMillan, Ainslie's understudy -the man who will helm the boat should Ainslie get ill or injured.
The two men have to be the same weight, so when Ainslie loses pounds, so must McMillan. He peruses the menu then cautiously picks a salad. 'If Ainslie loses any more bloody weight I'll starve to death,' he says.
We walk back from dinner that evening, through the deserted streets and past a clock on the harbour front that has been counting down to the start date for months. Grainy black and white photos of the snarling faces of the competing captains look out.
"I can't work out whether the clock terrifies me or excites me," says Ainslie. "There's so much to do, so many things that Land Rover could do to make the boat faster. In some ways I want loads more time, in other ways I'm ready and I want it all to start tomorrow."
