Prince George and his sister Princess Charlotte stole the show as they played in the grass while their father took part in a charity polo match.
Kate, the Duchess of Cambridge, kept a watchful eye on the playful siblings as they jumped and rolled around on the grass, while dad William was impressing on the field.
They were the centre of attention again, after delighting the crowds on the balcony of Buckingham Palace during Trooping the Colour on Saturday afternoon.
The rest of their weekend looks to have been much more relaxed, following their official engagement celebrating their great-grandmother's birthday.
The second day of the polo event did clash with Prince Philip's birthday, so the family was away while he marked turning 97, though he rarely celebrates his birthday.
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The brother and sister wore casual summer clothes, with Charlotte, three, showing off her pink sunglasses to match her sundress.
Prince George, four, played with his toy gun as the family sat on the grass together, alongside friends.
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He was also reunited with his cousin Savannah Philips, who was spotted covering Prince George's mouth during the national anthem as they stood on the balcony.
Kate wore a dress from Zara, costing £39.99, a far cry from the Alexander McQueen outfits she has stuck to for occasions like her brother-in-law's wedding and Saturday's Trooping the Colour.
She seemed to have comfortable heels on too, as she ran around with her children through the afternoon.
The Duchess was also spotted keeping an eye at the top of the helter skelter as the children tried out the fun fair rides.
William, a keen sportsman, was taking part in the Maserati Royal Charity Polo Trophy, in Tetbury, which raised money for two charities close to the prince.
He helped raise money for Centrepoint, of which he is a patron, and The Royal Marsden, of which he is president.
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Prince William, who played on the Maserati team, has regularly supported the Festival of Polo fundraising event at the Beaufort Polo Club.
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His team played Dhamani 1969 in the 3pm match.
The two-day event includes a celebrity match, a shopping village and a fun fair, and this year had a dressage session run by Laura Tomlinson MBE.
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