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Riding around on his scooter, five-year-old Kingston looked thrilled at the day out.
He and his little brother toured all the zoo's enclosures, including ‘Penguin Beach’, and took in a show at the amphitheatre.
It’s been a week of fun for the family.
On Monday, the singer invited Angelina Jolie and four of her six kids – Shiloh, five, Zahara, six, and three-year-old twins Vivienne and Knox – for a play date.
They spent a couple of hours in a face painting session at the London base Gwen shares with British husband Gavin Rossdale.