However, it wasn't long before Charlotte kicked off her shoes to run around the pitch barefoot.
Prince George wore a navy blue polo shirt with Khaki shorts while his sister Charlotte wore a pink floral frock.
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Of course, the Duke of Sussex has had plenty of cheeky moments over the years - the cute photo of him sticking out his tongue while in mum's arms at Trooping the Colour is an enduring one.
Theresa May's day of Brexit reckoning is coming, sooner or later
The government says the changes would weaken Britain's negotiating position and is seeking to reverse them in the Commons. The vote on Tuesday is the first of two days of debate that will test May's authority and her plans for leaving the EU.
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.
The event marked Prince Harry and Meghan Markle's first appearance together following their rumored honeymoon. The cheeky 3-year-old at one point showed off her handstand skills putting her mom into a fit of laughter.
Prince William was competing in the Maserati Royal Charity Polo Trophy in order to raise funds for both Royal Marsden Cancer Charity and Centrepoint, a foundation aimed at helping homeless young people.
But photos immediately after show Kate was actually running to greet England polo player Malcolm Borwick, who appeared to be beckoning her from beside the white marquees a few metres from the grass bank.
Vase discovered by chance in attic sells for €16.2million
The 16.2 million euros ($19.11 million) sale price included 2 million euros in auction costs and commissions. The sellers were unaware of the vase's importance or value until they took it into Sotheby's.
Kate kept a close eye on her little girl and oldest son, who spent much of the day chasing after each other and their cousin Savannah Phillips.
The incident brought back memories of the 2016 Trooping the Colour when William, 36, was scolded by Queen Elizabeth to stand up.
The next time the public is likely to see Prince Louis will be at his christening later this summer.
Doom: Eternal announced for PS4, Xbox One, and PC
Hugo Martin, creative director of Doom Eternal , and Marty Stratton, executive producer of Doom Eternal , to introduce the game. How long will you have to wait to rip and tear your way through a new host of demons? Sounds good to me; sign me right up.