Kate took the time to stop and chat to schoolchildren who were enjoying a day at the play area, as well as talking to the park's designer Robert Myers and others who worked on the project. "Just call me Kate", she said.
The mother-of-two was taken on a tour of the play area as she officially opened it and was shown some of its unique design features.
As the venue is particularly suited to youngsters, the conversation naturally turned to Kate and Prince William's two adorable children, Prince George and Princess Charlotte.
She met parents, charity executives, and donors helping to fund a planned £34 million "centre of excellence" for the Anna Freud Centre in King's Cross, London.
"Princess Kate!" the kids later chorused when she asked them what her name was.
Is Prince George responsible for attending to Marvin and his cage? Perhaps most stunning is Duchess Kate casually chic dressed in a lovely, long leather coat as she sits atop a bicycle.
The chairman of Historic Royal Palaces, Rupert Gavin, said that she was "bowled over" by the gardens.
We wonder how Ludo feels about the new royal pet!
The clothes Kate really set the tone for the day when she arrived for the photoshoot in jeans and a parka jacket, her hair in big rollers.
Taken by British photographer Josh Olins, the snaps were part of the Vogue 100: A Century Of Style exhibition.