Even a future king needs a little playtime!

Prince Georgeshowed his playful side during his dad,Prince William‘s charity polo match at Beaufort Park last Sunday.

“He leapt right into it. They first thing they did when they left the car was slide down the hill on his bum,” an onlooker tells PEOPLE. “He was peering over some hoarding around the side of the pitch, grinning at the others, who were messing around with him.”

Maserati Royal Charity Polo Trophy

Karwai Tang/WireImage

Maserati Royal Charity Polo Trophy

George, who usually appears to be on the quieter side (hehid behind dad William outside the chapelfollowingPrince Harry’s royal wedding), was full of energy and excitement as he darted off as soon as his feet touched the ground.

Samir Hussein/WireImage

Maserati Royal Charity Polo Trophy

Maserati Royal Charity Polo Trophy

He also goofed off with his older cousin, Savannah Phillips, 7, who famouslycovered his mouthwhile they were on the balcony for Trooping the Colour, which honorsQueen Elizabeth’s birthday.

Savannah Phillips and Prince George.James Whatling/MEGA

Trooping the Colour 2018

“Kate is a fantastic mum,” says the observer. “She was calm with the children.” Using a British phrase for “run loose,” the onlooker says, “She let them have their head.”

source: people.com