After deciding that the royal portrait her mother wants her to have done on her birthday is stuffy and promotes a fantasy to the public that she's no longer interested in, Margaret turns to a handsome, enigmatic photographer she recently met at a dinner party: Tony Armstrong-Jones. She goes to his studio, and after some unconventional behaviour from her future husband, he gets her to pose with the top of her dress pulled down from her shoulders; the resulting photo, while breathtaking, gives the impression that she's naked.
Although it appears to be Tony's idea to have Margaret wear her dress like that, the entire situation with the photo is a bold act of rebellion for the princess and a way for her to take back some agency in a life controlled by the royal family. She demands Tony send the portrait to the newspapers, where it's published for all to see. "It's a Margaret I've never seen before," Tony tells her after laying eyes on the photo for the first time. "That no one's ever seen before," she agrees, clearly stunned by the results.