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STORY: In a video released on Sunday, the heir to the throne handed out "Earthshot Burgers" to highlight the work of last year's winners of his annual Earthshot Prize, which he set up to help develop solutions to major environmental problems.

"Coming right up," the prince said as he served up the burgers to the stunned customers. "Morning everyone, nicely cooked, ready to go."

The object for William, who had teamed up with the founders of YouTube channel Sorted Food which reviews kitchen gadgets and shares recipes, was to raise the profile and work of three previous Earthshot prize winners.

"So the box you're about to eat in is built by a company called Notpla and there's no plastic involved, they've come up with a seaweed coating," the prince told the customers at the burger van.

"The ingredients inside the burger are grown from a greenhouse in India from a company called Kheyti, and last but not least, the way we cook them has been on a thing called Mukuru Clean Stoves, and that is designed by a lady in Kenya who came up with the concept to reduce air pollution."

He added: "Can't vouch for the taste, the quality but ... I'm rolling with it."