The two sisters made an elegant appearance at London's Kensington Gardens on Tuesday evening, where they mingled with a host of famous faces, including Bradley Cooper and Suki Waterhouse, Cara Delevingne, Keira Knightley and her husband James Righton and Pharrell Williams.
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Princess Beatrice and Princess Eugenie at the Serpentine Gallery Summer Party
Beatrice, 25, seems to have come into her own on the fashion front just recently, and she didn't disappoint in a white organza dress that was decorated with little flowers. She wore her flame-coloured hair swept back and injected a pop of colour with bright red lipstick.
Similarly, her younger sibling Eugenie, 24, also opted for a muted hue, choosing a pale blue sleeveless dress teamed with nude heels and natural-looking make-up.
Bradley Cooper and Suki Waterhouse
Also turning heads at the soiree - where guest were served signature cocktails by Eclipse Cocktail Bar - were loved-up couple Bradley and Suki. The film star, who was pictured partying at Glastonbury with Michael Fassbender and Noel Gallagher at the weekend, looked understandably delighted to be by his supermodel girlfriend's side as they attended the annual event together.
Suki, 22, looked stunning in a dusky pink Burberry Prorsum dress that featured a plunging neckline. On her feet she wore Topshop's chunky Loha platforms.
Alexa Chung, Keira Knightley and Cara Delevingne
Friend Cara Delevingne cut a striking figure in a sweeping black gown, while Gemma Arterton ensured she stood out from the crowd in a vibrant red two-piece.
Fashion favourite Keira Knightley chose an off-the-shoulder dress embellished with multi-coloured jewels and flowers, which fell into a white silk skirt. Little wonder that her husband of 14 months, James Righton, couldn't keep his eyes off the 29-year-old.
Keira Knightley and her husband James Righton
The Serpentine Gallery Summer Party is one of the highlights of the London social calendar. Every year for the past 14 years, the gallery has invited a celebrated architect to design a temporary pavilion outside the Serpentine, in Kensington Gardens, which is then unveiled at the summer party.
This year's pavilion, which has been designed by Chilean architect Smiljan Radic, is a fragile white fibreglass cocoon resting on top of a ring of boulders.