William, The Prince of Wales, shocked audience members watching the recording of The Graham Norton Show, drawing gasps as he appeared on the host's red sofa.
William made a surprise appearance on the chat show to talk about the Earthshot Prize, which he set up in 2020, and has five goals which an award is given - Protect and Restore Nature, Clean Our Air, Revive Our Oceans, Build a Waste-Free World and Fix Our Climate.
William appeared on the sofa alongside Cate Blanchett, Ted Lasso favourite Hannah Waddingham and Robert Irwin. Jorja Smith will also be seen on the show, performing her current single, Dancing.
Norton and the Prince discussed the need to pair optimism and urgency when tackling climate change, while the guests also spoke about William's support for Aston Villa and his love of Christopher Nolan's films.
This year's winners of the Earthshot Prize will be announced at a ceremony in Mumbai in November, with each winner receiving £1m.
Last year's winners were announced at a ceremony in Rio de Janeiro, with attendees including Kylie Minogue, Shawn Mendes, then-Prime Minister Keir Starmer, then-Energy Secretary Ed Miliband and London Mayor Sadiq Khan.
On the show, William said: "For many years I was hearing stories about environment issues and one thing that struck me was the negativity and doom which got me down.
"I thought we could do something more powerful and more optimistic and the idea of an awards' ceremony came about and we could talk about urgency and optimism together. It’s all about getting excited."
Next week's guests on The Graham Norton Show are set to include Michael Douglas, Glenn Close, Kieran Culkin, Naomi Ackie and the Sugababes - barring any more surprise royal appearances.
The Graham Norton Show airs tonight (Friday 23 October) at 10:40pm on BBC One.
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