Topshop has always had a strong celeb following, with the Olsen twins, Olivia Palermo and reality star Lauren Conrad all well-known devotees.
But this may well be the British-born brand's most high-profile fan to date.
The Duchess of Cambridge – who was spotted in a Topshop dress a few years ago (pictured) – reportedly browsed the store's High Street Kensington branch.
She spent just over £100 after waiting patiently in line just before the store closed.
Amongst her purchases were said to be a teal polka-dot skirt and a colbalt-blue jacket with velvet trim.
Kate also picked out a tiny pair of gold-effect leaf earrings that cost less than £10.
"She was low-key and casual – she seemed so normal," recalled the Topshop staff member who served her.
"She was really chilled out despite some customers in the queue behind her saying, 'Oh my God it's her' and pointing – she didn't seem fazed by it all and she was really sweet."
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Photo: © Rex