From gracing the stage as St Andrews University It-girl to eventually becoming Prince William's beautiful royal bride, the nation quickly developed an obsession with the way the Princess dressed - a phenomenon we now refer to as 'The Kate Effect'.
"Women around the world wanted to be Kate Middleton, and in the early days when Kate mostly favoured high street brands, her fans were able to emulate her, even if it was just a token nod," explains royal style expert, Miranda Holder.
"Kate manages to tread that awkward line between fashion and the restrictive etiquette limitations of the working royal perfectly - and all this makes utterly compelling viewing, keeping us hooked."
Inspired by thrifty Princess Anne, Kate has followed suit in becoming one of the most prolific outfit repeaters in the royal family, often choosing to rewear clothes from her twenties, and even recycling most-memorable gowns for red carpet appearances.
In 2023, the mother-of-three surprised the nation when she attended the BAFTAs wearing the same dress she had worn to the event four years earlier. In November, she sparked joy in a bow-adorned hat on Remembrance Sunday that had first been worn to Prince William's graduation from Sandhurst in 2006 before they were married.
From rocking reworked Alexander McQueen to upcycling former flattering fits, Kate's stance on sustainable fashion continues to position her as an icon of environmental dressing.
Here, see her best outfit repeats of the last twenty years.