Prince William has shocked unsuspecting members of the public at a food truck in London when he appeared as the server handing out veggie burgers.

The heir to the British throne teamed up with Youtube channel Sorted Food to create the meat-free burger, which was made using the environmental innovations of the 2022 winners of The Earthshot Prize.

In a video uploaded to the channel on Sunday, the Sorted Food team were shown preparing the burgers using Earthshot items handed to them by Prince William, before heading out to serve them to diners from a food truck.

When a member of the team asked the "chef" for four Earthshot burgers, Prince William turned around, revealing himself to gasping customers.

"Of all the things I was expecting, it was not that," said one woman in the video, later asking others, "What just happened?"

"My brain took like three seconds to buffer," added one man. "Am I dreaming? Have I had enough sleep?"

"I was lost for words," another diner said.

William told customers that the Earthshot Prize, a 10-year project which he founded in 2020, aims to "repair and restore the planet."

The prize recognizes those providing forward-thinking environmental solutions across five categories: "Protect and Restore Nature," "Clean Our Air," "Revive Our Oceans," "Build a Waste Free World," and "Fix Our Climate."

"Being joined at our studio and in the food truck by Prince William was a real 'pinch me' moment -- hearing him explain how passionate he is about helping the planet and what the Earthshot Prize is doing was incredibly inspiring, and has already given us a lot of ideas for future projects to work on with our community," said Jamie Spafford, co-founder of Sorted Food, in the release.

The Sorted Food team made the plant-based burgers using vegetables typical of what would be grown in Kheyti's Greenhouse-in-a-box. The Indian start-up's innovation is designed for small-hold farmers, offering their crops shelter from unpredictable elements and destructive pests, according to the prize's website.

The team then cooked the food using Mukuru Clean Stoves, launched by Charlot Magayi in Kenya in 2017. When burning, they create 90% less pollution than an open fire and 70% less than a traditional cookstove, according to the prize's website.

The burgers were then served in Notpla food boxes, which are made from seaweed and plants instead of plastic.