Self-Portrait, the small label designed by Han Chong and founded just three years ago, has rapidly ascended to label-of-choice for It girls everywhere, for events formal and casual alike. The designs are known for their lace panels, pastel colors, and ultra-feminine details, occasionally punctuated by a bit of an edge — a funky hem here, a flash of skin there. Even when not in pastels, the darker designs are still frilly and delicate. For the brand's most recent collection, there were even some asymmetrical and slightly unfinished details (hemlines come detached, shoulders not quite held together). And now, Chong's devoted cadre of It girls includes a real-life princess.

Kate Middleton at the premiere of 'A Street Cat Named Bob' in London, England, November 2016

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Who: Catherine, Duchess of Cambridge. Alias Kate Middleton.

When: Thursday, November 3.

Where: The premiere of A Street Cat Named Bob, benefitting the in London, England.

What: A white, floor-length gown by Self-Portrait with a geometric-patterned eyelet bodice and long sleeves and a loose pleated skirt with a near-invisible thigh-high slit, Oscar De La Renta earrings, a Mulberry clutch, and cabernet-colored Gianvito Rossi pumps.

Why: A bit bolder than Catherine usually goes — wedding dress by Sarah Burton for Alexander McQueen aside, she tends to select buttoned-up options from Dolce & Gabbana, Erdem, and Jenny Packham. This Self-Portrait design has a sheer lace bodice — very Buckingham Palace proper — and a thigh-high slit in its pleated skirt, nearly invisible under the layers of fabric until it blows, Marilyn Monroe-like, around the Duchess of Cambridge's ankles. It manages to be both in perfect line with her personal style, prim and preppy as it may be, while also being glamorous enough for a film premiere. The burgundy shoes offset the springtime freshness of the look with a darker autumn tone, setting off a similar shade in her clutch. She's not a movie star, but on this night, she fits right in.