Lily took to the stage at the Royal Albert Hall for the City Rocks gig, which was held to raise money for Coram - the oldest children's charity, and had to be sewn into her risqué outfit beforehand.
But despite the added help of a needle and thread, Lily still seriously flashed the flesh!
Lily's dress is from William Vintage and featured sequins and beading across a skin-coloured panel stretched across her chest.
It had a long black skirt, which Lily teamed with nude heels, and she completed her look by plaiting her dark hair across her head.
Before the concert started, Lily took a selfie while she was being stitched into her frock by a seamstress.
Posting it on Instagram, the mum-of-two commented: "Being sewn in." Then, after wowing the crowd on stage, Lily tweeted: "That was dope. Thanks guys x x."
We're still surprised Lily didn't slip out of her dress. Clearly she's got one good seamstress!