The King was presented with a special hand-knitted cake to mark 10 years of his charity's textiles education programmes.
Charles looked delighted with the two-tier, woollen cake complete with colourful, crafted decorations and knitted candles and piping, which was presented alongside an assortment of knitted cupcakes.
Future Textiles was set up by The King's Foundation in 2014 after being inspired by Charles to address the skills gap in the UK textiles industry through education and training.
A decade on, more than 7,000 people have benefited from its courses, with projects run in collaboration with high profile brands and firms such as Chanel and Yoox Net-a-Porter.
Members of Knitwise, sessions run by Future Textiles to develop locally based high-skilled hand-knitters, presented the King with the unique celebratory cake at the charity's annual graduation event at its Dumfries House headquarters in Ayrshire, Scotland, last month.
The anniversary is also being marked by an exhibition at the Garrison Chapel in London, which regularly hosts showcases by Foundation students, with the cake on public display, alongside a range of garments made by alumni over the last 10 years.
Other Future Textiles projects include the 10-month, paid Modern Artisan initiative, which gives fashion and textile graduates the chance to design and make a sustainable, luxury line of outfits using heritage skills for the Yoox Net-A-Porter for The King's Foundation label.
Jacqueline Farrell, education director at the King's Foundation, said: "Initially, Future Textiles benefitted secondary school age pupils by introducing them to the beauty of making and ensuring they understood the technical sewing and craft processes that are so vital to responsible fashion design and manufacturing.
"Due to the incredible support of the industry and our partners, the programme grew rapidly and now offers a huge range of courses ranging from day workshops and weekly community groups, to full-time courses which provide students with the skills needed to start their own businesses and gain employment in the industry."
She added: "We are proud to count among our graduates talented artisans now making their mark in the fashion industry as key practitioners for some of the world's best-known brands, and founders of businesses that promote sustainability through long-lasting, high-quality garments and products."