Paul Smith, Gabriela HearstJojo Korsh/BFA.com

Gabriela Hearst and Sir Paul Smith took over the penthouse at Chateau Marmont to celebrate the launch of their limited-edition collaboration, drawing an eclectic crowd that included Jessica Alba, John Boyega, Edward Norton, Quinta Brunson, Michael Stipe, Diplo, Tom Parker Bowles, and Mamie Gummer.

On paper, the Uruguayan designer and British fashion savant might make for an unlikely pair. Alas, the duo had been put in touch by a mutual friend—Wesley Schultz of The Lumineers—who sensed they’d hit it off. They became pen pals at first, trading notes on each other’s work, and then one day, over text, the idea of collaborating was floated. “It was not a big plan,” Smith told Vogue. “In the world today, everything’s so corporate and homogenized. This was just like, ‘Should we do something fun together?’”

Inspiration struck thanks to a box of Smith’s father’s old photographs. An amateur photographer, his images of the Welsh mountains had faded due to time and decades spent in storage. “I describe them in my head as like a Godard film,” Smith said. “Slightly hazy, slightly in focus, and slightly out of focus; they have a very surreal tint.” For Hearst, who grew up on a ranch where her grandmother was a formative presence, the images resonated immediately—and the images became the cohesive thread of the collection.

The result is a 14-piece offering for men and women, featuring the vintage visuals transposed onto silk trench coats, bias-cut slip dresses, intarsia cashmere sweaters, and virgin wool barré suiting. The nappa leather Nina and Demi bags got the landscape treatment too. “Color is everything,” noted Hearst. “Working with the master of it, the images already said so much. You can see them in embroidered intarsia, hand-knitted into a cashmere sweater, and then also on a suit.” Said sweaters are hand-knit by Manos del Uruguay—a nonprofit cooperative supporting economic independence for women in rural communities—in a nod that speaks directly to Hearst’s longstanding commitment to responsible production.

Guests took their seats for a rooftop dinner of hamachi crudo, beet salad, and lemon tagliatelle at tables dressed in white linen and laden with colorful Louis Poulsen lamps; cashmere Manos del Uruguay throws draped over the back of each chair. Quinta Brunson, wearing the slip dress and trench coat, summed up the appeal. “It’s the simplicity and care of Gabriela’s work, but with the color and spark of what Paul has always done. It’s a really magical collaboration and I’ve been complimented on my outfit about 20 times.”

While they dined, the collection was already moving—several pieces had sold out in boutiques that day. And as the last of the tiramisu disappeared and the party dispersed, Hearst told everyone to pocket their napkins—as they too were printed with images from the collection. “Paul has the joyfulness of a kid with the humbleness of one of the greats,” praised Hearst of her collaborator as she kissed cheeks and said her goodbyes. “He’s one of the original punks.”