London – They clearly have the competitive streak that exists between many a young brother and sister.
Prince George and Princess Charlotte showed their sibling rivalry as they took a turn on the dodgems.
George, five, seemed delighted as he whizzed around in his inflatable bumper car, while Charlotte, three, gritted her teeth and furrowed her brow before bursting out laughing.
One onlooker, who saw the pair and their cousin Mia Tindall, five, on the fairground ride, said of the little princess: "She was either giggling with glee or totally focused on what she was doing. It was hilarious to watch."
Mia, daughter of former England rugby player Mike Tindall and wife Zara, also showed a competitive instinct, comparing heights with George.
In a purple puffer jacket, jeans and white baseball cap with a pink heart on it, she grinned and stretched up to touch the forehead of her taller cousin, who is six months older, as Charlotte and the Duchess of Cambridge looked on. George, in a khaki fleece, dark green jeans and trainers, wielded a plastic sword as he rode on the shoulders of Mr Tindall.
The Duke of Cambridge carried Mia, who took off her coat despite the chilly weather, while Kate, in tight black jeans and a Barbour quilted jacket, held the hand of Charlotte, who wore a tartan skirt and blue jacket.
The royals spent the day together at the Burnham Market international horse trials in Norfolk on Friday, where Zara, 37, was competing. The onlooker said: "The kids had a great time and the parents enjoyed themselves too. They looked like two ordinary families having fun on a day out."