Technically, that headline isn't correct. The only person wearing a dress, that being Florence, actually looked quite presentable. A bit underwater sea nypmh, but pretty nonetheless. 

Everybody else looked like hookers from 1991. Apart from Rita Ora, she wore her jammies. Leona Lewis was more Madonna circa True Blue, while Jessie J embodied the bottom half of Beetle Juice. Unfortunately she's more limber than Michael Keaton. Azealia Banks arrived more Evil Eye avec Foot 'n Mouth wellies, but soon fulfilled the hooker spec once onstage. Nikki Minaj was more circus ringleader meets carousel horse.

OK, so the hooker from 1991 description only extends as far as Azealia Banks onstage, Fearne Cotton's jeans and - quelle surprise - Rihanna.

First she wore this on Saturday night when she performed with Jay-Z. And then she ditched the snorkle goggles and the hotpants for butbag pants, fishnet bicycle shorts and a mantelpiece over her sunglasses.  

Understandable you don't want to look your best beside Jay-Z given Beyonce slapped you with a "dressing room ban" but this is really going above and beyond the call of duty