The royal tot, accompanied by mom Catherine, Duchess of Cambridge and sister Princess Charlotte, was photographed playing on a grassy hill at the Maserati Polo match at the Beaufort Polo Club in Gloucestershire on June 10.
The Maserati polo match was just one of many Prince William, alongside brother Prince Harry, will play during the English summer as they do every year to raise money for charity.
The Duchess of Cambridge was like any mum on a day out, with small children lounging all over her! Little Charlotte adorably practiced her headstands in front of mother Kate, and was even sporting a pair of very cool sunglasses.
It looks as though the toy gun came as part of a classic "police set" as the youngsters can also be seen with a plastic baton and some handcuffs and Prince George is known to have a fascination with the police and emergency services.
Autumn Phillips and her children, Savannah and Isla, joined the royals.
Charlotte and George were reunited with their cousins.
But the smiles soon turned to tears, as her mum had to step in and console her with a cuddle.
During the daytime event, George and Charlotte stole the show as they ran through the grass playing tag, hopped over wooden beams, and figured out how exactly a slinky can provide entertainment.
During the polo match, the Phillips girls joined Charlotte and George in their sideline antics.
Prince William and Kate Middleton's four year old son appeared to be in a mischievous mood as he stood on the balcony of Buckingham Palace with the rest of his family, including Princess Charlotte, talking the whole way through the National Anthem.