Trading her sequin-tinged stage costumes for lighter fare, Beyoncé stepped out wearing new designer Sies Marjan Saturday night in London. A sartorial endorsement from Beyoncé is a rarity among the younger, relatively unknown designer set. The frock, a white ruffle-heavy number, is part of the brand’s first collection, which debuted at New York Fashion Week in February.

“How incredible to have Beyoncé as our first ever celebrity to wear Sies Marjan?” the label’s creative director Sander Lak gushed via e-mail exclusively to WWD. (As a testament to the scale of his brand, the designer’s Instagram of the sighting only had 139 likes six hours after post.) “When I saw the picture, I did a little dance and put ‘Lemonade’ on loud!”

Beyoncé gave the garment her own twist. Originally styled on the runway as a tunic half-tucked into a mulberry calf-length skirt, the Queen showed off her gams wearing it à la carte. Her tight braids left in from the night’s performance segued into her look as they untwisted to reveal her natural wave. Linking hands with Jay Z, she was perfectly accessorized.

In the thick of her global “Formation World” tour, Beyoncé wore the look on her way to a post-show drink at Harry’s Bar, London’s exclusive, members-only club. The club enforces a strict dress code, but the doors swung open to welcome Beyoncé and Jay Z.

Lak, former design at Dries Van Noten, debuted the Sies Marjan fall collection to largely positive reviews. (WWD concluded its write-up with “It was all very, very cool.”) His Van Noten roots are clear in his proclivity for naturalism, splashy colors and printed flourish. He was given a seed investment by Nancy and Howard Marks to build his luxury label from scratch and it would seem it’s paying off — Beyoncé is not a bad start.