LONDON: Celebrities joined Prince William in London on Sunday for the inaugural awards ceremony of his Earthshot Prize, an ambitious environmental program that aims to find new ideas and technologies around the world to tackle climate change and Earth's most pressing challenges.

The winners announced Sunday included the government of Costa Rica, which was honored for a project that pays local citizens to restore natural ecosystems, and the city of Milan, which was handed a prize for its Food Waste Hubs program, which recovers food from supermarkets and restaurants and distributes it to those in need.