What counts as "cool" exactly? It's not easy to pin down: as a notion, "coolness" is both frustratingly intangible and constantly in flux. In fashion, music and cinema, the genesis of "cool" feels heavily tied to the emergence of popular culture in the 20th Century – from the US jazz scene that first popularised the term, to the fashion world's post-war development of ready-to-wear clothing aimed at the newly emerging teenage market, as well as mass media such as pop music and cinema that became the dominant modes of creative expression in the same period.

If there's any one element that defines "cool", it's perhaps a sense of calm confidence – a quality desirable enough to encourage emulation. This feels especially true in cinema, where films, filmmakers and performers labelled "cool" over the years are heavily copied. From the films of Jean-Luc Godard to classic Hollywood stars such as James Dean and Marlon Brando, "cool" in cinema has often been a mixture of fashion, flair and finesse.