Pippa Middleton may have been dressing down on Monday afternoon, but Kate's younger sister still looked as chic as can be, wearing one of her favourite tartan coats by Alexa Chung. Underneath her swish outerwear staple, she rocked a classic all black ensemble, which included a cosy roll neck, and finished off the look with crisp white trainers by Jimmy Choo.
READ: Pippa Middleton and Kate's matching jewellery moment revealed
In photographs that appeared on the MailOnline, the mother-of-two wore her brunette mane in a sleek ponytail and went makeup free for the London outing. Gorgeous!
WATCH: A decade of Pippa Middleton's Style
Kate and Pippa are seen as some of the best-dressed sister duos ever and their styles are actually pretty similar. Both have been spotted through the years in belted trench coats, enjoy high-end maternity label Seraphine when they are with child, love a bit of nautical fashion, and are big fans of lacy frocks from Self Portrait.
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It was thought that her sister Kate celebrated her special birthday at her and Prince William's Norfolk abode, Anmer Hall, with her family and three children Prince George, Princess Charlotte and Prince Louis.
We are still reeling over the 40th birthday portraits of the royal that were released to the public on her big day. Duchess Kate wore Alexander McQueen for the occasion - the same designer who created her wedding dress. The pictures were taken by royal photographer Paolo Reversi.
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Black Dogtooth Long Formal Coat, £26.39, New Look
Kate's natural beauty was highlighted with a subtle makeup look consisting of light blush, rosy pink lips and minimal eye makeup. Her flowing brunette hair was teased into loose waves, framing her pretty features.
Jimmy Choo Hawaii crystal-embellished perforated leather sneakers, £350, Net-A-Porter
READ: Princess Beatrice and Pippa Middleton unexpectedly twin for royal night out
The three stunning shots will form part of the permanent collection of the National Portrait Gallery which re-opens in 2023 following re-development work.
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