Style Steal - Alexa Chung
In the above picture, Alexa is wearing a dress by Open Ceremony. The dress would cost you quite bit, but luckily for you, I have found something very similar and much cheaper.
New Look sell a white lace zip back prom dress for only £28, and its also available in black (below). So theres no need to break the bank to look like Alexa. If you look hard enough, you can find anything for cheaper!