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Sizzling and safe, classic and edgy, entrance-making and elegant, the little black dress is the most adaptable weapon in the female arsenal. And Princess Beatrice knows it. The 24-year-old royal reached for an LBD to attend a book launch party in London last night with boyfriend Dave Clark, who works at Sir Richard Branson’s Virgin Galactic space tourism project. She accessorized the look with a studded belt and matching accessories, including a black braided clutch and pumps. What’s the key to a perfect LBD? Says designer Julie Chaiken: “It should be fabulous enough to turn heads in a room and sophisticated enough to take the breath away of someone special.” Did Beatrice’s do the trick? You tell us.

Plus, see more of Princess Beatrice’s outfits.

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Roksanda Ilincic’s “Izumi” dress is a go-to dress this season. Princess Beatrice, 23, paired the British designer’s piece with sky-high cobalt Nicholas Kirkwood platforms and a pink Anya Hindmarch clutch at the 2012 Britain Creates party in London in June. The next week, Marisa Tomei took the style for a spin during Men’s Fashion Week in Paris, where the 47-year-old actress matched the shift’s electric cuffs to her Aperlai peep-toes. “Women should follow their heart and feel comfortable in what they’re wearing,” Ilincic, shown inset, told InStyle.com. “You should feel empowered, and always add a personal touch—your own personality to the garment.” It looks like these ladies did just that! The style is available $1,300 at farfetch.com. Plus, see more stars who love Roksanda Ilincic in the gallery.

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•  Princess Beatrice: A Year of Style
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It’s been quite a year for Princess Beatrice! Last April, she made headlines when she showed up to her cousin Prince William’s wedding with a ribbon fascinator perched atop her head, an accessory that went on to launch endless conversation and more than 40 Facebook groups. (Eventually, she auctioned it off for charity.) Ever since, the York princess—with the help of her trusty new stylist, Charlie Anderson—has stepped up her style, whipping out couture outfits one after another. Click through the gallery to see for yourself.

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What happened in 2011? Princess Beatrice‘s fascinator went viral, Rihanna made a case for sheer clothing, and Demi Lovato pulled a Kriss Kross and wore her gown backwards. See the biggest celebrity style risks of the year in the gallery now.

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• The Prettiest Dresses of the Year
• Hottest Trends of 2011
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