She could of danced all night with Rex Harrison. In "My Fair Lady," Audrey described the ‘absolutely divine dress’ that Cecil Beaton designed for the transformed cockney flower girl to wear at the ball. ’All I had to do was walk down the stairs. The dress is what made me do it.’ When she put on the glittering beaded dress, she became Lady Eliza.."(taken from the book Audrey Style).
Cecil Beaton portrait of Aubrey Hepburn dressed in a costume he designed for her in her role in My Fair Lady, although this particular dress didn't make into the film. Beaton won an Oscar for her costume design and art direction for My Fair Lady.