Prince Charles quipped that he "struggles" to keep his measurements the same
Prince Charles
Credit: Chris Jackson/Getty

Prince Charles says staying fit is a “never-ending battle.”

Queen Elizabeth‘s eldest son paid a solo visit to Gloucester workshop of Emma Willis, who has been making shirts for him for many years. When he was gifted a new garment, he joked that staying the same size wasn’t easy.

“Very kind of you — you’ve got my measurements. I struggle to keep them the same, a never-ending battle,” he quipped.

In addition to a tour of the factory floor and the cutting room, the 71-year-old royal met with injured service personnel sponsored by the company’s charity Style for Soldiers.

“I just wanted to come really to thank you, more than anything, for the wonderful things you do, apart from making fantastic shirts and boxer shorts and everything else. But everything you do for our armed forces and all those who had the horror of being wounded in one way or another, it is a wonderful thing you do,” Prince Charles said.

Prince Charles
Prince Charles
| Credit: Chris Jackson/Getty

Willis recalled six years ago, when one of Charles’ dressers said the royal would like to try her designs.

“So I went to Clarence House and measured His Royal Highness for the first time, and we’ve been making his shirts ever since,” she said. “And one of the things we specialize in is very fine Swiss cottons, and he loves lovely soft fabrics.”

Prince Charles
Prince Charles

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Prince Charles is collaborating with Vin + Omi, a British fashion brand with punk roots, known for combining avant-garde fashion with sustainable innovation.

We love working with Prince Charles, and we have a lot of fun doing it,” co-founder of the brand Omi tells PEOPLE from his London studio, adding, “He has been very involved in terms of what we are doing, and it’s an ongoing relationship, which is really lovely.”

This will be their second collaboration with the royal household – the award-winning designers previously harvested more than 3000 nettle plants from his Highgrove estate in Gloucestershire for their Spring/Summer 2020 collection last September. Now their current collection which will show during London Fashion Week includes hydrangeas, nettles, willow, ash, wood chippings and horse hair clippings from the stables, all of which has been donated by the royal.

“He is very aware of the materials and it’s quite humbling – people call us pioneers of sustainability, and then you meet someone like Prince Charles and he knows so much,” says Omi, who along with Vin (the design duo go by their first names only) met Charles for dinner just two weeks ago at Dumfries House, the stately home in Scotland that serves as the headquarters of Charles’ charity The Prince’s Foundation.

“Sometimes I can’t believe I’m talking to the future King of England – even to be having conversations around sustainability is bizarre because you would think that someone so privileged wouldn’t be interested, but he is very learned.” With the duo’s punk ideology, the collaboration is not one that they could have predicted. “Our whole brand ethos is against everything that comes with establishment, but it’s amazing that something as simple as the environment can link different people together.”