The Harper's Bazaar UK Women of the Year Awards [1] celebrate accomplishments in the arts, philanthropy, and fashion, so it was no surprise that guests at Tuesday evening's awards were immaculately dressed in a whole host of formal looks, many of them from British designers. The ladies of Downton Abbey led the charge, with breakthrough award winner Lily James wearing romantic Erdem and television icon winner Michelle Dockery resplendent in a couture jumpsuit by Ralph & Russo.

Elsewhere, Kate Winslet [2], Nicole Kidman [3], and best actress winner Sienna Miller [4] added some Hollywood glamour. Read on to see the most glamorous looks from the evening in our gallery.

Kate Winslet

Kate wore a Roland Mouret dress with Stephen Webster jewelry.

Sienna Miller

Sienna wore a Valentino gown.

Nicole Kidman

Nicole wore a Proenza Schouler dress and jewelry by Berganza Ltd.

Michelle Dockery

Michelle's Ralph & Russo jumpsuit featured a plunging back detail.

Lily James

Lily wore an Erdem dress.

Ellie Goulding

Ellie wore a Stella McCartney gown.

Lara Stone

Lara wore a Givenchy outfit.

Ruth Wilson

Ruth picked a little black dress.

Clémence Poésy

Clémence wore a Chloé dress.

Sophie, Countess of Wessex

Sophie, Countess of Wessex, picked a Mary Katrantzou dress with intricate details on top.

Karen Elson

Karen wore a Chloé gown and Cartier jewelry.

Erin O'Connor

Erin wore a Roksanda dress.