Once upon a time (about a decade ago), expats newly arrived in London (like yours truly) quickly learned that the place to shop was Temperley London in W11. Alice Temperley was the cool girl's designer because that is exactly what she was herself: the pinup for cool. Shoppers flocked to her Notting Hill outpost for a bit of tea and comfort in the form of thick knits and cozy gypsy looks—clothes that telegraphed the English rose, après-hunt thing, even on non-English-rose types. It was a lifestyle, not just a sweater. But now, with her new Spring collection, all that has changed—or, more accurately, it's been revved up.

These days, Temperley is casting her net out to a wider international clientele. Some of it may have to do with dressing the Duchess of Cambridge, and by doing so, helping to put Kate (never mind herself) on this year's Vanity Fair International Best-Dressed List. Indeed, her appeal has a borderless following. On a recent visit to Doha, Qatar, we saw women go mental in her store (there's really no other way to describe it), while neighboring shops stayed empty. The appointment of Ulrik Garde Due, formerly of Georg Jensen, Burberry, and Céline, to CEO is part of a strategic plan to grow the brand.

Temperley's Spring collection, inspired by a holiday in Sicily, should go a long way toward doing the same, without alienating her fans. Key pieces included trapeze shapes and a new way to deliver a bolero jacket, with sleeves that were structured and flowy at the same time. But, as always, it was the surface details—the rose damask fabrics, the complete symmetry of the embroidered flowers on organza, the crystal embellishments, and the cherry-blossom prints—that seduced. Temperley has such a sure hand, she even made a leopard print mixed with a lilac floral look good. Her challenge going forward will be maintaining this momentum.