Sienna Miller's Back Bares All

Which blonde beauty is trailing cotton on the spikes of her Christian Louboutin boots? Bonus points if you know how/why is got stuck there! Game’s over! Congrats to mld627 for getting it right first!

Pictured: (left) Sienna Miller at The Orange British Academy Film Awards at the Royal Opera House on Sunday, Feb. 11 in London, England. (right) Sienna Miller spends a night out at the Ivy in London, trailing bits of cotton on her heels! Check out more pictures of Sienna after the jump!