LONDON — Celebrities joined Prince William in London on Sunday for the inaugural awards ceremony of his Earthshot Prize, an ambitious environmental program aimed at finding new ideas and technologies around the world to tackle climate change and Earth’s most pressing challenges.

Actors Emma Thompson, Emma Watson and David Oyelowo joined Kate, the Duchess of Cambridge, in handing out the awards at Alexandra Palace in north London.

Prizes went to the Republic of Costa Rica; Takachar, a New Delhi company; Coral Vita, Bahamas; the City of Milan Food Waste Hubs, Italy; and AEM Electrolyser (Germany/Thailand/Italy). Each winner will receive a grant worth $1.4 million to develop and scale up their ideas.

William and his charity, The Royal Foundation, launched the Earthshot Prize last year, inspired by President John F. Kennedy’s 1962 “Moonshot” speech that challenged and inspired Americans to go to the moon.

“There’s been lots of amazing ideas over the past decades but it’s the implementation that really counts, so that’s what this is all about. So it’s really a reason to be cheerful,” Thompson said.

In a pre-recorded short video, William said: “We are alive in the most consequential time in human history.”

“The actions we choose or choose not to take in the next 10 years will determine the fate of the planet for the next 1,000,” he said.

“Many of the answers are already out there,” he added. “But we need everyone, from all parts of society. to raise their ambition and unite in repairing our planet.”

The finalists included a 14-year-old student who proposes using solar energy to replace charcoal to power millions of roadside ironing carts in India; a community project in Congo devoted to protecting gorillas; and a Kenyan enterprise that turns organic waste into fertilizer and insect protein for farmers.

The ceremony comes days ahead of the COP26 U.N. climate change summit in Glasgow, which begins on Oct. 31.