Prince William, the Duke of Cambridge, surprised diners in south London by serving environmentally-friendly burgers from a food truck.

In a video released on Sunday, the prince teamed up with the founders of the YouTube channel Sorted Food to raise awareness of the work of three previous Earthshot Prize winners. The Earthshot Prize, established by Prince William, awards grants to individuals and organizations developing solutions to major environmental problems.

The Earthshot burgers were served in biodegradable boxes from a company called Notpla, which uses a seaweed coating instead of plastic.

The burger ingredients were grown in an Indian greenhouse by a company called Kheyti, and the burgers were cooked using Mukuru Clean Stoves, designed by a Kenyan woman to reduce air pollution.

Diners were left astonished by the surprise encounter with the prince, and the experience left them inspired to take action in their own lives.