The stunning actress rivalled the likes of Ellie Goulding and Lily James who were both clad in the most attention grabbing gowns and proved her amazing fashion credentials in this absolutely beautiful, backless concertina dress emblazoned with tens of the pink birds.
Sienna floated effortlessly along the red carpet in the frock which looked like it had been plucked straight out of a fairytale and glammed it up with a stand-out, viken-like matte red lip.
Gah, we love her.
It was a successful evening for the stunning Brit who scooped a Women of The Year award at the swanky bash held in London's world-famous Claridges hotel after having a blast with good pals Kate Winslet, Lara Stone and a scantily clad Nicole Kidman.
Now that's a squad we'd kill to be a part of.
Rocking a duck-egg blue clutch and a dazzling gold leaf bracelet, svelte Sienna remained in her show-stopping number throughout the evening unlike Ms. Goulding who dipped into her wardrobe for a much shorter hem come the after party!
We're hunting down a similar number, pronto.
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