In 1966, Nigel Davies noticed the young Lesley Hornby and offered her a modelling contract. She was only 16 and weighed 6½ stone (41 kg, 90 lbs). Davies advised her to go by her childhood nickname, Twiggy, and renamed himself Justin de Villeneuve. After sweeping England as "The Face of '66" when her modelling pictures, taken by Barry Lategan, were made public, Twiggy arrived in New York in March 1967. It was believed that the Twiggy craze would die down within a month; Twiggy, however, became an instant icon and supermodel. Known for the high fashion mod look created by Mary Quant, Twiggy changed the world of fashion with her short-haired androgynous look. Her style has dominated the runways for forty years. She was also famous for drawing long, fake eyelashes under her bottom lashes. These are, unsurprisingly, named Twiggys.

Twiggy was regarded as one of the faces of 1960s Swinging London, along with other models, such as Jean Shrimpton and Celia Hammond.