The 25-year-old showed off her slender figure in a smart monochrome ensemble featuring a high-waisted short black skirt, a white top with embellished collar, a black sequin jacket and patent pumps.
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With her distinctive red locks left to fall loosely around her shoulders, Beatrice opted for natural makeup that accentuated her fresh complexion and striking green eyes.
While the Queen's granddaughter went for a classic look, other guests at the VIP event chose to stand out in more daring ensembles.
The fashion retrospective is a biography, in clothes, of Isabella Blow — the woman who liked to tell her own story in hats.
Her favourite memory of her mother, who famously offered her 14-year-old daughter a formal handshake on the day she left home, was being allowed to try on her pink hat. And the story she liked to tell about meeting her husband Detmar Blow began with him complimenting her hat.
Liberty Ross and Mary J. Blige
Fashion was the great love of London-born Isabella's life, and, following her death in 2007, the exhibition aims to cement her deserved place in fashion history.
In honour of the flamboyant grande dame, Liberty Ross showcased her flawless frame in a colourful striped dress, which she teamed with a furry white coat and a towering purple fascinator.
Mary J Blige was dressed for the occasion in a tartan pencil skirt and patent boots, while Gemma Arterton chose a super short embellished grey mini dress and a blazer jacket.
Isabella's close friend Daphne Guinness helped coordinate the exhibition after buying up the collection in 2007 in a bid to stop the designer pieces being sold at auction.
"The decision to put Isabella's wardrobe on display was a natural progression; it felt like what she would have wanted," Daphne told Vogue.
"I bought the collection because I couldn't bear for it to be dispersed; it was her life's work — her legacy. What better way of celebrating that legacy than allowing the world to view it."