The littlest Princess, wearing some pretty sunglasses, left her mum in fits of giggles later on, as she attempted a headstand near the grassy verge the Duchess was sat on.
Kate attending the event was a surprise, so fans were delighted when she joined the match with George and Charlotte, sitting with cousin-in-law Autumn Phillips, who brought her children as well.
Kate then congratulated the rest of the team at the Beaufort Polo Club with hugs - and more kisses - as she weaved her way to her husband, Prince William.
Princess Charlotte, 3, doesn't always accompany her parents during royal press tours, but when she does she is just as fashionable as her mum.
Savannah Phillips trying to shut up Prince George.
The third-in-line to the throne was photographed playing with the gun with a friend in the grass.
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Princess Charlotte performed gymnastics barefoot during the polo match.
The match, which will see the Maserati team take on the Dhamani 1969 side, is part of the two-day Gloucestershire Festival of Polo, hosted by Beaufort Polo Club from 9th-10th June.
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"Spending quality time together is such an important aspect of family life and for me, as a mother, it is the simple family moments like playing outside together that I cherish".
It was a busy weekend for the Cambridges this weekend as they had Trooping the Colour on Saturday.
The tournament was Prince William's first sporting appearance since the couple welcomed Prince Louis earlier this year.