Ben Ainslie and his British Land Rover BAR team were forced to fend off a last-race challenge from holder Oracle Team USA before claiming overall victory in the America's Cup World Series event in Portsmouth Sunday. The win also takes the home team to the top of the 2016 series leaderboard. An exciting day of action at Southsea featured the high performance AC45 foiling catamarans unleashing their breath-taking speeds and closed with a nail-biting finale where Spithill and Ainslie, Oracle teammates at the last America's Cup in 2013, locked horns in fierce opposition. Spithill nailed the start and led the fleet to the end, but Ainslie kept the pressure on and crossed the line in second, which gave him the overall win by a single point. From the opening leg in the first race, Ainslie looked comfortable in the stronger breezes in the Solent, where Land Rover BAR train daily, and made the most of another great start by speeding off to the first mark at a rapid 25 knots. A little over 12 minutes later, the race was over with Ainslie crossing the line to the sound of excited applause from the massive British crowds, including the Duke and Duchess of Cambridge. The resounding win boosted their score by 20 points and extended their lead at the top of the table to five points over Oracle. But a comeback by the Americans in the second race, in which Spithill turned on the aggression in the stronger winds and upped his speed, saw them claim a 10-second win. It closed the gap between Oracle and the British and meant the result hinged entirely on the final race. Oracle started well and kept Ainslie successfully at arm's length. Going into Sunday, it was the British and French team Groupama Team France who had dominated all the action on the water. But Franck Cammas struggled to master the bigger breeze and dropped down the rankings to post two disappointing last places and a fifth to finish in fifth place overall. Emirates Team New Zealand, series leader before Portsmouth but without its star sailors Peter Burling and Blair Tuke, dropped down to fourth. Softbank Japan finished in third and Iain Percy's Artemis Team was floundering in last place after a dismal event.