Inspired by Sienna's favourite go-to party dress, the ultra-mini shift has that vintage quality she's most known for, combined with modern touches such as the deep armholes. Like her very own dress, this is a look you can wear year after year thanks to its classic styling - think Sixties shift meets intricate Art Deco work of art. M&S X SIENNA MILLER Womens M&S X SIENNA MILLER Sequin Mini Dress