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The 25-year-old royal sported a stylish black blouse and an eye-catching patterned skirt from ASOS for the fashionable occasion.
Beatrice accessorised her outfit with sheer tights, buckled heels and a red leather bag, wearing her auburn hair in loose waves.
The Princess, who was supporting the launch of Mrs Alice at the Palace, was joined at the luxury London department store by Poppy Delevingne, Guy Pelly, Tamara Beckwith and blogger Alice Naylor-Leyland.
Poppy and Cara Delevingne are picture-perfect bridesmaids for sister Chloe
Poppy wore a floral printed skirt, a black t-shirt and denim shirt. The 27-year-old added a leather jacket, black ankle boots and a white Prada handbag to complete her look.
Prince Harry's ex-girlfriend Florence Brudenell-Bruce marries
Florence, who looked chic in leather trousers, a white blouse and a beaded waistcoat, showed off her glittering wedding ring.
Florence tied the knot with multi-millionaire Henry St George in a romantic ceremony in the south of France in July 2013.
While Beatrice and her high society pals were out and about in London, the royal's sister Princess Eugenie and mother Sarah, Duchess of York were in New York.
The mother-daughter duo made a glamorous appearance at the Gavel & Grand Benefit Auction at the Big Apple's upmarket Bowery Hotel.
Princess Eugenie joined in New York by mum Sarah, Duchess of York on pre-Mother’s Day outing
Eugenie - who turned 24 last week - looked chic in a long-sleeved grey dress paired with silver jewellery while her mum picked a simple black dress to showed off the results of her recent three stone weight loss.