The American actress made a surprise appearance at the star-studded event, taking to the stage to present the International Designer of the Year award to Miuccia Prada.
The mother-of-two, 41, showed off her toned physique in a plum and pink colour block dress that featured a black pleated skirt. She accessorised with Boucheron silver drop earrings and strappy black sandals and kept her make-up natural.
She was joined at the British Fashion Awards by fellow celebrity Sienna Miller.
The actress, 31, was stunning in a silk emerald Burberry gown that she teamed with a white shearling jacket and silver Burberry heels. The outfit was fitting for the star, who is currently the face of the British brand.
Sienna was showing off a different beauty look, rocking pale pink hair. She was accompanied to the ceremony by her fiancé Tom Sturridge before the pair attended the Playboy 60th anniversary party.
The party was also in celebration of Kate Moss appearing on the cover.
Supermodel Kate also attended both events. At the fashion awards, she was honoured for her services and success in the industry for over the past 25 years.
Handing out the Special Recognition Award to his friend, Marc Jacobs said, "London might have two Kates, but in my mind there is only one."
Accepting the prize, Kate said, "Oh my god it's so weird, very very surreal. Thank you everyone who has worked with and kept booking me. I am really very grateful, thank you!"
One Direction star Harry Styles was also honoured at the event, picking up the British Style Award.
Voted for by the public, the 19-year-old heartthrob fought off tough competition from David Beckham and former flame Cara Delevingne to scoop the prize.
Also at the awards ceremony were Alexa Chung, Pixie Geldof and Poppy Delevingne.
Poppy, who recently celebrated her hen do, looked lovely in a white Emilia Wickstead shirt dress that featured a piano motif.
Best pal Alexa was typically chic in a white, one-shouldered dress, while Pixie opted for a pale blue silk slip dress.