William made the mistake of talking up his chances before heading out - when Catherine wished him luck, he retorted, "It's not luck, it's skill."
The Duke was in NZL68, the old training monohull Team NZ used in the lead-up to the 2007 challenge. The Duchess was in NZL41, built for the 1995 America's Cup for the Japanese Nippon Syndicate before it was bought by the Great Britain challenge.
Wills, alongside Grant Dalton, appeared to go for the strategy that sticking his tongue out in concentration and leaning forward over the helm would make the boat go faster.
The British tabloids rather unkindly dubbed Kate "Waitey Katey" as the couple's courtship dragged out with no sign of an engagement ring. This time, she had no intention of waiting.
A canny tack by her team and a hitch with a sail on her husband's boat undid all William's hard work in the first race. It was Kate who sailed across the line first with a fist held aloft in triumph, before turning to her husband's boat with a rather gloating expression on her face.
The second race did little to restore William's honour - he was whipped again and Kate finally got revenge for the time he beat her while dragon-boating in Canada.
He handled it with some grace after he managed to get his grinning wife back from Barker.
"We were sabotaged," he told her as Dalton tried out the excuse of royal protocol, saying the Palace had decreed the Duchess must win.
The republicans didn't let the occasion slip by, sending up a plane banner with "Time for a Kiwi head of state" on it. But for all the feel-good factor that might rub off on the Prime Minister, there were signs that the visit may have done some harm to his campaign to change the flag. When the royals stepped out yesterday, there was not a silver fern to be seen - it was all the red, white and blue of the Union Jack and the New Zealand flag. Prince George wasn't there, but he also took a prize - a child-sized Sea Legs amphibious craft, which may cost the Crown a bit in excess baggage when the family leave.
The biggest winner of the day was Barker. Not only does the win break a rather long losing streak, but he did it with "the best-looking crew" he'd ever captained. As for William, Team New Zealand possibly didn't help his ego any by pointing out on its blog that the match had another similarity to the real America's Cup: "There was no second. Team Duke is unlikely to debrief the racing tonight."
In the space of a day, the Prince of Sails went to Prince of Wails.