The Duke and Duchess of Cambridge and their children welcomed the legendary naturalist to Kensington Palace, meeting him outside in the garden after school on September 24.
Photographs shared by the royal couple show seven-year-old George and Charlotte, five, looking almost starstruck by their encounter with the TV star, apparently to the amusement of their parents and their special guest.
WATCH: Royal children begin their first days at school
And Sir David, 94, did not disappoint his young hosts – presenting Prince George with the fossilised tooth of a giant shark that he excavated himself during a family holiday in Malta in the late 1960s.
The fossil, from a carcharocles megalodon or 'big tooth', was embedded in the island’s soft yellow limestone, which was laid down during the Miocene period some 23 million years ago.
The species is believed to have grown up to 15 metres in length, which is about twice as long as a Great White shark.
Prince George was very impressed with his shark tooth (Photo: The Duchess of Cambridge)
In another photograph, George is seen excitedly examining the tooth, as his little brother Louis, sitting alongside their father, looks on.
A source told Hello!: "It was very sweet, all three children were playing with it."
Sir David was at the Palace to watch his new film, A Life on our Planet, with the Duke. Instead of attending a glittering premiere for the feature-length documentary, the two men sat together in the garden at Kensington Palace, both under blankets to protect them from the chilly autumn weather.
Aides had set out two director’s chairs with their names on, but the Duke and Sir David decided to sit in the wrong ones.
Prince George, Princess Charlotte and Prince Louis meet their idol (Photo: The Duchess of Cambridge)
In what he has called his "witness statement", the veteran broadcaster shares some of the defining moments of his career and the devastating changes he has seen.
David Attenborough: A Life on Our Planet is showing in cinemas from 28 September and on Netflix from 4 October. He and Prince William have joined forces regularly in the past, most recently in January, when Sir David narrated the announcement of the Earthshot Prize.
The multi-million pound initiative aims to find 50 solutions to our greatest environmental problems over the next decade and Kensington Palace is set to announce more details in the coming days.
Prince William and Sir David Attenborough watched his new film (Photo: The Duchess of Cambridge)
William and Kate are also seen chatting to Sir David in a new ITV documentary which airs on October 5, with the Duchess saying of her children: "They’re massive fans."
In Prince William: A Planet for Us All, the Duke says becoming a father to Prince George, seven, Princess Charlotte, five, and two-year-old Prince Louis has spurred him on to do more to save the planet.
"I have always loved nature, but fatherhood has given me a new sense of purpose,” he says. “Now I’ve got George, Charlotte and Louis in my life, your outlook does change. You want to hand over to the next generation, the wildlife, in a much better condition."
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