Cardigans have officially dusted off their granny reputations, a renaissance that was led by Miuccia Prada and her revamped button-up cardis. This week at a Jimmy Choo party in London Alexa proved that a cardigan can look surprisingly sexy, wearing her red heart-stitched cardigan with nothing underneath except a black bra and the top button left open. No longer just dowdy cover ups, Alexa proves that cardigans make the most impact when worn as their own tops. It could be easy for a cardigan to look a little scruffy at a party, so it's important to get the mix just right. Alexa paired hers with a pair of black straight leg, cropped leather trousers and elegant Jimmy Choo heels with polka dot mesh inserts. Keep scrolling to see how Alexa Chung managed to make a cardigan look sexy.