Emma Watson just wore her most political outfit yet

Last night's groundbreaking Earthshot Prize Awards, held in London's Alexandra Palace, were a rousing success.

For an event designed by Prince William to 'incentivise change and help to repair our planet over the next ten years', it was only fitting that there be a green carpet instead of a red one, and that guests make sustainable sartorial choices.

Two such guests included The Duchess of Cambridge Kate Middleton, who recycled this dress for the occasion, as well activist Emma Watson.

The Harry Potter actor has long been an advocate for sustainable fashion, partnering with brands such as People Tree to promote ethical clothes.

During the promotion for her movie Cinderella in 2018, she even launched her Press Tour Instagram account, where she shared her outfits from the tour, each chosen for their sustainable credentials.

These included a Miu Miu dress made by trusted suppliers and artisans locally in Italy, as well as a Dior dress created using certified organic silk and an Emilia Wickstead gown made from unwanted fabric.

She even previously told Vogue, 'I will work for anyone for free if they're prepared to make their clothing fair trade and organic,' referring to the fact actors often get paid by designers to wear their creations on the red carpet.

For this particular event, Emma chose to make a statement with a custom Harris Reed outfit with an unusual back story.

The demi-couture gown is a custom up-cycled piece from the the Harris Reed FOUND. collection, which consists of 10 looks entirely made from clothes donate to Oxfam charity shops. It was created in partnership with the charity to raise awareness of Second Hand September, which encourages shoppers not to buy anything new for a month.

One piece from the young designer's collection, which was presented at London Fashion Week, was also donated to Oxfam and sold in its Selfridges pop-up, with all proceeds going to the charity.

Emma's cream gown top is actually made from up-cycled bridal wear, and she paired it with the brand's signature H-flared trousers, as well as some chunky boots.