The monarch squeezed in the front row, chatting with American Vogue editor Anna Wintour, who wore her trademark sunglasses, and presented an award recognising British design excellence.
The lucky recipient was Richard Quinn, a recent fashion graduate of Central Saint Martins who started his own label in 2016 and has quickly earned recognition as part of the next wave of talented young British designers.
The 91-year-old monarch gave the London-based Quinn the first Queen Elizabeth II Award for British Design. She took to the catwalk to address the crowd and honor Quinn, who was chosen for the prize by the British Fashion Council.
"As a tribute to the industry, and as my legacy to all those who have contributed to British fashion, I would like to present this award for new, young talent."
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The queen, who seemed to enjoy the spectacle, wore an Angela Kelly duck egg blue tweed dress and jacket detailed with tiny Swarovski crystals and black gloves.
She also toured showrooms before presenting the award on the final day of fashion week, which brought hundreds of designers, buyers and journalists to London for a series of catwalk displays highlighted by Christopher Bailey's farewell show at Burberry.
The gala was attended by model Naomi Campbell, designer Stella McCartney and other luminaries of the fashion scene.