5-year-old George can be seen marching around with a cheeky smile on his face, while usually outgoing Charlotte took a back seat to her big brother - before later posing up a storm for photographers.
“George is a real star, quite the little chap,” a source told People. “He was having a great time, running around like the leader of the pack.”
Mum Kate, who is still on maternity leave after welcoming son Prince Louis back in April, opted for bold blue for the occasion in a Catherine Walker & Co coatdress and blue floral headpiece.
George and Charlotte were part of the official wedding party and wore traditional outfits in blue and white ensembles by Amaia.