Unlike all of the other famous guests who donned the usual floaty frock and strappy sandal combo, the former Made in Chelsea star slipped into a beautiful, midnight blue velvet playsuit from celeb style favourite William Vintage.
Proving that she could give Victoria's Secret models Kendall Jenner and Gigi Hadid a run for their angel wings, a super-bronzed Millie was all smiles in the plunging one-piece which boasted ruffle cuffs, teeny-tiny shorts and a waist-tie that nipped her in.
Hot is an understatement.
With her honey-hued locks styled into voluminous, glossy waves Mills, took her 70s-inspired retro look to new heights and showed off her cool boot-court hybrid heels as she sashayed past the dazzled paparazzi.
Even though she stepped out without hubby Professor Green, Millie schmoozed with the likes of beauty vlogger Tanya Burr, a crimson-clad Pixie Lott and model Amber Le Bon at the event which took place at London's Victoria & Albert Museum.
We can't get enough of her.
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