While the work of the Earthshot Awards is very important, we must talk about Princess Catherine's outfit. In keeping with the event's sustainable theme (guests were specifically asked not to purchase new attire for the evening), Catherine rented an off-the-shoulder green gown from HURR (a British designer dress rental platform). Her dress was by Solace London, and she paired it with sparkling Gianvito Rossi pumps (opens in new tab) and, perhaps the ultimate re-wear item, an emerald and diamond choker that once belonged to her late mother-in-law, Princess Diana. This is the emerald and diamond choker that Princess Diana wore many times.

Princess Catherine also wore emerald and diamond earrings from Asprey, and William reappeared in a blue velvet blazer that we have seen before.

The choker, however...

Diana wore it as a necklace, but it was also famously worn as a headband when she and then-husband Prince Charles toured Australia in 1985.

People reported that "Diana's decision to wear it as a headpiece was accidental. According to royal biographer Kitty Kelly, she tried to wear it over her head instead of around her neck, but the choker got stuck. She liked the way it felt when worn over her forehead so much that she decided to wear it that way that night."

The piece was originally a gift to Queen Mary in 1911 and passed from Queen Elizabeth to Diana after her marriage to Prince Charles. Diana's vast jewelry collection, as well as various other pieces, was given to her two sons, both of whose wives frequently wear Diana's work (in the case of Catherine, Princess of Wales, who wears her iconic sapphire and diamond engagement ring daily). (In the case of Catherine, she wears her iconic sapphire and diamond engagement ring every day).