The Duchess of Edinburgh attended the premiere of King Charles's environmental documentary at Windsor Castle on Wednesday evening without her husband by her side.
Prince Edward's absence from the star-studded screening of "Finding Harmony" went unexplained, with Sophie arriving solo to support the monarch's passion project.
She was joined at the event by the Duke and Duchess of Gloucester, as well as King Charles and Queen Camilla.
The Waterloo Chamber at Windsor Castle was transformed into a lavish cinema for what became one of the royal residence's most glamorous gatherings in recent memory.
Duchess of Edinburgh stuns in £1,350 dress at Windsor Castle as Prince Edward absent
|GETTY
Sophie made a sustainable fashion statement by recycling a striking emerald-green Galvan Margot silk-satin midi dress she had previously worn to a London film premiere six years earlier.
The elegant gown, originally priced at £1,350, featured a flattering high neckline and ankle-skimming hemline.
The 61-year-old mother of two accessorised with brown Prada heels and an £8,370 diamond bracelet from Chopard.
She completed her ensemble with a gold brooch pinned to the dress, diamond earrings, and wore her hair swept up in a sophisticated updo.
The Duchess of Edinburgh's dress was first worn in 2020
|PA
Her makeup remained soft and dewy for the occasion.
The former PR executive proved a natural at working the room, engaging in animated conversation with Oscar-winning actress Kate Winslet, who narrated the documentary and led the celebrity arrivals.
Sophie was also spotted chatting with Benedict Cumberbatch, who attended alongside his wife Sophie Hunter, as well as Dame Judi Dench and Stanley Tucci.
Sir Rod Stewart was among the famous faces at the premiere, putting on an affectionate display with his wife Penny Lancaster.
The Duchess of Edinburgh speaking to Kate Winslet
|PA
LATEST ROYAL NEWS:
The Duchess of Edinburgh chatting to Stanley Tucci and Judi Dench
|PA
The Princess of Wales was notably absent from the gathering, leaving Sophie to charm the King's A-list guests at Windsor Castle's first-ever film premiere.
The 90-minute documentary delves into the origins and scientific foundations of the King's "harmony" philosophy, which he outlined in his 2010 book of the same name.
Footage shows Charles collecting eggs from chickens at the "Cluckingham Palace" coop on his Highgrove estate, where he reveals his fondness for crispy baked potatoes, declaring "red Duke of Yorks" the finest variety.
The monarch reflected on his decades of environmental advocacy, stating: "I just felt this was the approach that I was going to stick to. A course I set, and I wasn't going to be diverted from."
The film will launch on Prime Video across more than 240 countries on February 6.