Prince William and Kate Middleton promoted sustainable clothing with their outfit choices while attending the inaugural Earthshot Prize event on Sunday evening.

The Duke of Cambridge arrived at his ambitious environmental programme in a dark green velvet blazer that he previously wore at an anniversary gala for charity Centrepoint in 2019. He ditched his usual crisp shirt for a dark polo neck top, and paired it with black trousers that he first wore 20 years ago. He finished off the look with black Oxford shows.

Meanwhile, the Duchess of Cambridge wore a lilac Alexander McQueen dress featuring a gold beaded waistband that was made for her in 2011 for the BAFTA dinner in Los Angeles. She paired the outfit with beautiful Kiki McDonough special edition morganite earrings.

The star-studded guest list at the event was asked not to purchase new clothes for the programme and "consider the environment when choosing their outfit." Presenter Emma Thompson said that she was relieved after she was informed about the dress code, and decided to come in the suit and the badge that signifies her damehood, which she wore when she last saw Prince William at Buckingham Palace.

In a symbolic move, no stars had flown to London from other cities to attend the event. William and Kate also chose an electric Audi car to travel to the event.

The next event of the Earthshot Prize, which will award five winners each year for a decade for solutions that substantially help the environment, will be held in the United States next year. This year's five awards were won by Protect and Restore Nature: The Republic of Costa Rica; Clean Our Air: Takachar, India; Revive Our Oceans: Coral Vita, the Bahamas; Build A Waste-free World: Milan's Food Waste Hubs; and Fix Our Climate: AEM Electrolyser, Thailand, Germany and Italy. Each of the winners received £1million prize money and a global network of support to scale their cutting-edge environmental solutions to repair our planet.

At the end of the event, William took to the stage to tell the audience: "I want to say something to the young watching tonight. For too long, we haven't done enough to protect the planet for your future, the Earthshot is for you. In the next 10 years, we are going to act. We are going to find the solutions to repair our planet."

Wearing this Alexander McQueen floor-length gown to the BAFTA Brits event in Los Angeles in July 2011, Kate floored the fashion world in style. The same year, Catherine topped Vanity Fair's best-dressed list for the first time. (Photo: Reuters)
Kate Middleton previously wore this Alexander McQueen floor-length gown to the BAFTA Brits event in Los Angeles in July 2011. (Photo: Reuters)
Prince William Prince Harry British Royal Family Kate Middleton