Jenny Packham creates jawdroppers: the types of decadent, vintage-inspired gowns that land celebrities such as Sandra Bullock and Angelina Jolie on best-dressed lists. “All I ever aim to do is make beautiful eveningwear,” Packham tells me over the phone from her studio in London. “I don’t like things that are uncomfortable—everything we do, however structured or detailed, needs to be made so that when someone wears it, they completely forget about it.”

It’s this effortless appeal that seems to have caught the eye of Packham’s most famous fan, Kate Middleton. The Duchess of Cambridge has worn her designs on no fewer than 10 public occasions. In fact, after Middleton chose Packham’s cornflower-blue polka-dot crepe-de-Chine dress to introduce newborn Prince George to the world, demand for the frock crashed Packham’s website for days. “I’m not really allowed to talk about Kate Middleton,” says Packham apologetically. “It’s very, very thrilling that she has worn our dresses, but that’s all I’m allowed to say.”

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Packham was interested in design from a young age. “Both of my grandmothers were needlewomen, so I grew up around dress design,” she says. She attended London’s Central Saint Martins and founded her collection in 1988—in November, Packham celebrated her label’s 25th anniversary. “It’s funny; in fashion you can never relax and feel like it’s all sorted,” she muses. “Every season, you have to give yourself a challenge and come up with something new and fresh.”

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Packham’s fall/winter 2013 collection was inspired by the Salonnières, 17th-century Parisienne nobility. “They were cultured women who would arrange soirees that were a bit like early feminist get-togethers,” she explains. “They would gather in the most decadent houses in Paris and discuss their ideas.” Packham expressed this inspiration through relaxed gowns and separates in petrol blues and deep reds. “It’s nice to have a personality behind the collection,” she says. “This time, it was a luscious, intelligent socialite, which is a nice muse to have!”

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