Exclusive: Royal-Favorite Designer Anna Mason Is the It Girl British Label You're Probably Sleeping On

If you've followed royal fashion for long, you know that some brands end up feeling very "been there, done that" after a while. During my recent trip to Royal Ascot, I spotted plenty of lovely, yet predictable looks—and if I was given a pound every time someone wore one particular label, I could've bought myself a decent bottle of champagne. But one British brand you might not have heard of yet has become a quiet force on the royal fashion scene. Enter: Anna Mason.

Although I've seen her romantic floral prints on Pippa Middleton and Zara Tindall, my first encounter with Anna Mason's clothing was in London last month, when I met the designer at her Chelsea boutique. When I tried on the dreamiest pale green silk blouse, it was love at first sight—and after seeing the craftsmanship that goes into these pieces, it's easy to understand why members of the Royal Family are choosing to wear Anna Mason time and time again.

"I think what draws Zara and and Pippa and anyone really to my aesthetic is that it's just so feminine, and also they're really easy to wear," Mason tells me during her July Hamptons pop-up, held at The HUB in Bridgehampton through the end of the month. The Princess of Wales is also an Anna Mason fan, and although she hasn't worn the pieces publicly, I'm told she owns a skirt, trousers and other items.

Princess Anne's daughter, Zara Tindall, has worn Anna Mason dresses to Royal Ascot on several occasions, including last month, when she wore the designer's white floral Heloise midi on day two of the races. Mason shares that Tindall "wants to work with as many British brands as possible, which is really great."

For Mason, wearability is key, especially when high-profile women are stepping out in her designs. "Although they look quite formal, they are constructed in a way that's really comfortable and very female body-conscious," she notes of her clothing. Details like pockets add to this "sense of security," and Mason—who offers both ready-to-wear and made-to-order pieces—shares that she while many of her clothing is unlined, she'll often make a silk slip for a member of the Royal Family "to avoid any moment of feeling at all conscious."

"I definitely feel a responsibility when dressing women connected to the Royal Family," she says. "I want them to go out there feeling their very best." Mason keeps the specific fashion "stipulations" the royals have in mind when considering her design elements, too.

"It's interesting to work with people who have to have a much more formal approach to their dressing, because their stipulations are quite a lot more in depth than ordinary women, as it were," she says, pointing out that making wider straps and more modest cuts ensures "that everything is suitable for the sorts of events that a customer or a member of the Royal Family might want to wear them for," such as Royal Ascot.

Part of the beauty of Mason's designs is those finer details, like the intricate pleats hidden under puffed sleeves, which she calls an "old-fashioned" approach to craftsmanship. The designer also flies the flag for English lace whenever possible, using "one of the last English lacemakers."

She tells Marie Claire that when it comes to the Royal Family or celebrities wearing her designs, it makes "all the difference."

"The thing about all of this is that British brands, we start so small, usually, that any exposure that we can get from these people is so helpful to our brand profile," she says. "It just, it does wonders, really, in a way that nothing else does."