Led by four-time Olympic gold medal winner, Ben Ainslie, and watched by the Duke and Duchess of Cambridge, the UK team held on for a second place finish in the final race of the day to seal the series win.
Reiging America's Cup champion, Oracle Team USA, had pushed the home favorites all the way having won Sunday's second race to pile on the pressure.
But Land Rover Bar's overall win ensures they move to the top of the series leaderboard.
"The whole last race was really tense," Ainslie said in comments carried by the AFP news agency.
"Oracle were trying to get us down the fleet so the guys did a good job defending that and sailed really well.
"We hung in there and were delighted to get the second place.
"It was quite emotional because you don't often get the chance to race in front of a big crowd at home and to get the win meant a lot to us."
Oracle Team USA skipper Jimmy Spithill said he did everything possible to stop Ainslie and his crew.
"We did everything we could without risking throwing the lead away," said Spithill.
"Downwind there wasn't much we could do but upwind we were smashing straight onto the front of him and slowing him up and trying to get another team up.
"But the third or fourth placed boats weren't close enough to put enough pressure on."
Ainslie, is hoping to lead a British team to a first America's Cup win in the event's 165 years.
The World Series competition is being held over the course of 2015 and 2016 before the 35th edition of the America's at Great Hamilton, Bermuda, next year.