It is the first time we have heard Louis, now two and a half, speak in public, and the most we have ever heard from George, seven, or five-year-old Charlotte.
The Duke and Duchess of Cambridge's three children were filmed by their parents in the garden at Kensington Palace last month, each asking a question, with the veteran naturalist recording his answers separately.
WATCH: The Cambridge children appeared in the adorable new video
Looking so grown up, Prince George goes first, saying: "Hello David Attenborough, what animal do you think will become extinct next?"
Princess Charlotte, her hair tied back in a ponytail and still wearing her school uniform, says: "Hello David Attenborough, I like spiders, do you like spiders too?
But it's their little brother Louis who steals the show, taking a deep breath before asking, "What animal do you like?"
Watch the clip above to hear their voices and David's incredible answers!
Prince George, Princess Charlotte and Prince Louis later met Sir David in person
Celebrities including David Beckham, Billie Eilish and Dame Judi Dench have also put their questions to Sir David via video to coincide with the launch of his film in cinemas and, from Sunday 4 October, on Netflix.
The Cambridge trio, who according to their mother Kate are "massive fans" of Sir David, recorded their questions for him before they got the chance to meet him in person on September 24, when he spent an afternoon watching his new film David Attenborough: A Life on This Planet with Prince William in the garden at Kensington Palace.
George was given a fossilised shark's tooth during the meeting
George, Charlotte and Louis were pictured looking starstruck at their encounter and all three children were fascinated by a fossilised shark's tooth Sir David brought as a gift for Prince George.
A source told HELLO!: "It was very sweet, all three children were playing with it."
Last year George, now seven, was captured on camera as he visited his mother's RHS Back to Nature Garden at the Chelsea Flower Show, giving it a rating of "twenty" out of 10.
Prince George and Charlotte were previously heard speaking during a visit to the Chelsea Flower Show
Charlotte, then four, delighted royal watchers when she exclaimed "Ooh la la!" in delight as she explored the garden with her siblings.
And at their baby brother's Christening in July 2018, three-year-old Charlotte sternly told photographers outside the Chapel Royal at St James’s Palace: "You're not coming."