What look is conjured up when you hear the name "Sienna Miller"? Her iconic vintage boho looks that defined early noughties festival fashion? (The studded belt owes more to the actress than it could ever repay.) Or perhaps her achingly covetable Anatomy of a Scandal wardrobe which focused on understated elegance, boasting pieces by the likes of Cefinn, Victoria Beckham and Max Mara?
Whatever it is that springs to mind, we can almost certainly guarantee that it will be worlds apart from her latest look, worn to accompany her at one of London's most festive hotspots.
MORE: Sienna Miller makes a case for autumn pastels as she strolls around NYC
Sienna turned back the clocks on Wednesday night as she attended Claridge's annual Christmas tree party, serving 1980s fashion royalty. Branching out drastically from her trademark contemporary chic, the actress defied convention and instead went for pieces that felt distinctly retro-reminiscent.
The 40-year-old rocked up in a black cold-shoulder mini puffball dress by Simone Rocha – a style that was hugely popular in the 1980s – with voluminous sleeves, a gathered skirt and floor-length ties. Continuing with her vintage-inspired theme, Sienna went for the decade's lifeblood accessory: leg warmers.
Sienna's stockings-esque iteration felt super unique, featuring a subtle geometric pattern and circular cut-outs, and stretching from the bridge of her foot all the way to her mid-thigh. She paired her unconventional accessory with Jimmy Choo's Heloise platforms, utterly fitting given the occasion.
The event was held to mark this year's version of Claridge's iconic Christmas tree, designed by Jimmy Choo's creative director Sandra Choi. Produced in collaboration with set designer Simon Costin, the diamond-inspired reflective creation stands over five metres tall and allows guests to actually step inside and experience the tree on an immersive level.
READ: Sienna Miller street style: 7 of her classic looks for eternal fashion inspiration
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"I have always said I would love to know what it is like to step inside a diamond, and now I can! To be able to collaborate with Simon Costin on this incredible project has been an honour," explains Sandra.
"The jewel has been a repeated metaphor I have used to describe Jimmy Choo, not just because they are used in our designs, but for the multifaceted nature of the collections we create as well as the reflection and light we want to bring. The power to transform and shine bright."
Speaking of shining bright, Sienna's sartorial ability is absolutely beaming, and we can't wait to see what she has in-store for the rest of the party season…
The lust-have
Heloise velvet platform sandals, £695, Jimmy Choo
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The must-have
Black velvet bow platform heels, £55, River Island
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