Kate, dressed in a light blue open shoulder dress and wedges, was pictured sitting on the grass with George and Charlotte playing next to her.
But pictures from the day depicting George brandishing a toy gun cast a shadow on an otherwise happy day.
"Without a shadow of a doubt, the loveliest moment of #TroopingtheColour today: Savannah Phillips conducted the band during the National Anthem, then hushed her cousin, Prince George (the future King) when he started to chat".
The moment has been captured, with people going gaga over this royal Tow Sawyer-like child, also giving a flawless throwback to the time Prince Harry shared a similar moment with Princess Beatrice. "THAT is #girlpower", one person wrote.
Adrina Price commented: 'Sad to see George playing with a gun when the whole country has a gun/knife crime situation.
Part of the event was an open house for the emergency services that included an air ambulance vehicle that interested Prince George. My American side here, biased maybe b/c of everyday #gunviolence in United States of America, but my British side agrees.
She also played a game of tag with her older brother, Prince George. No child in this day and age should look at any gun as a fun toy.
In perhaps the most candid snaps of the three royals ever seen, royal fans witnessed an adorable glimpse into normal family life for the Cambridges - showing they really are just like everyone else.
While George seemed elated throughout, he was constantly talking, disturbing the elder cousin, who was seen telling him to stop, while the little one smiled sheepishly at the chiding.
What do you think about the toy gun? Malcolm is said to have a close relationship with the Royal Family and has played alongside Prince Harry at the Sentebale Charity Cup.