Prince George looked on from the sidelines as Prince William and the Duchess of Cambridge fought against a host of celebrities. Photo / Getty Images
There was competition on the high seas, a comical prize-giving, and one very realistic pirate. In short: everything needed for a fun family day out.
So when the Duke and Duchess of Cambridge went to work to raise a million pounds for charity in their inaugural King's Cup sailing race, it was just as well Prince George and Princess Charlotte were on hand to make it a day to remember.
The royal children stole the show on the Isle of Wight as a gap-toothed Prince George sported a sailor's hat to watch the Duke and Duchess do battle on the seas and, apparently, "ate his first ant".
The 4-year-old Princess staged her own amusing mutiny on the balcony, encouraged to wave to the crowds above the prizegiving stage but choosing to stick her tongue out mischievously instead.
If the famously competitive Duchess hoped to show them how mummy can beat daddy at sport, she was sadly mistaken, left with a giant wooden spoon as her team was disqualified.
The Duke's team came joint third, picking up a bottle of champagne for charity Child Bereavement as his wife took her defeat in good spirits.
The King's Cup, a royal sailing tradition that dates back to George IV that has now been revived by the Cambridges, is intended to raise money for eight charities, with the Duke and Duchess joined by six celebrity ambassadors representing Centrepoint, the London Air Ambulance, Tusk, Action for Addiction, Place2Be and the Anna Freud Centre to race head-to-head.
The Duke raced for Child Bereavement UK, while the Duchess competed for the Royal Foundation and its focus on early years development.
While the Duchess is the more experienced sailor, having learned as a child, her crew finished last in the two-stage race after coming seventh in the first leg and being disqualified in the second.
The boat, along with six others, crossed the starting line too early and was supposed to go back, but instead carried on with the race regardless.
As it crossed the finish line, the race commentator noted: "Duchess of Cambridge! Great job. Unfortunately disqualified."
The Duke's team came joint third with the boat from Centrepoint. Tusk, represented by Bear Grylls, came in first, and the London Air Ambulance, captained by Dan Snow, in second.
Prince George and Princess Charlotte, wearing nautical-themed blue outfits, were looked after by maternal grandparents Michael and Carole Middleton for the day, spending the morning at a local fair to take part in a tug'o'war, balloon and bubble making, and learning how to be a pirate.
Their baby brother Prince Louis was also on the island, but was kept out of sight of the cameras while the two older children were taken on a boat to watch the race.
Appearing at the prize-giving, where Princess Charlotte left her mother and grandmother laughing in mock-shock after poking her tongue out at the crowd, the two children saw their mother cheerfully pick up an enormous wooden spoon as a booby prize.
As the Duchess shook her head, compère Dan Snow said: "This is the first time the Duchess has ever finished last in anything, I can guarantee. So you'd better enjoy it because it will never happen again."
Accepting the winners' trophy, Grylls spoke of the "incredible work" of Tusk and praised the Duke and Duchess' "vision and inspiration" in setting up the event.
In an unexpected aside, he added from the stage: "And also, Prince George: your first ant you ate today! And that is a great moment. Well done you. What a guy!"
Earlier in the day, George and Charlotte joined in family fun on the island as part of the festival, where their team, nicknamed "The Scallywags", won a tug of war during a session with entertainer Pirate Pete.
"We've got a fine bunch of buccaneers on our hands," Pirate Pete said afterwards.
"Us pirates, we're not used to hanging around royalty, we're not usually best friends. But I've had a good day recruiting some new pirates."
Asked whether the royal children had a "natural aptitude for piracy", he added: "Oh yes. They were trying to steal my weapons, and there were some good pirate faces being pulled.
"They were really charming and excitable. They're just the same as any other kids, that's what's nice: they want to have fun, be imaginative, play."