When Swedish designer Filippa Knutsson launched her eponymous label 25 years ago, “Scandinavian minimalism” was simply a way of describing a place and a style—not shorthand for a global aesthetic. Now, the stars have aligned for Filippa K: Its aesthetic, one of stripped-back luxury, is perennially in fashion, and its ethos of sustainability is in the ascendant. From her home in North London, Knutsson—who recently returned to the helm after five years away from the company she founded—talks to Harriet Fitch Little about how her designs still jump off the rails after a quarter century, and the importance of a little bit of bad taste.

You founded Filippa K in the early 1990s. What made it the right moment to launch a minimalist clothing line?
It was a reaction to the ’80s, whi...