[1] He became well-known to film audiences for his portrayal of secret agent Lemmy Caution and other, similar pulp heroes in French B-movies of the 1950s and 1960s.

His celebrity and status as something of a pop icon saw him work with prominent arthouse directors like Jean-Luc Godard (as Caution in Alphaville and Germany Year 90 Nine Zero), Rainer Werner Fassbinder (as himself in Beware of a Holy Whore 1971 and also World on a Wire), Jesús Franco, Agnès Varda, Rosa von Praunheim, Lars von Trier, William Klein and Mika Kaurismäki.

[4] Having failed to make a career in the United States, Constantine returned to Europe in the early 1950s and started singing and performing in Paris cabarets.

[5] In the 1950s, Constantine was a star in France because of his role as the hard-boiled detective/secret agent Lemmy Caution (from Peter Cheyney's novels) in a series of French B-pictures, including La môme vert-de-gris (1953), This Man Is Dangerous (1953), Je suis un sentimental (1955), Lemmy pour les dames (1961) and Your Turn, Darling (1963).

Constantine later claimed that he had never taken his acting career seriously, as he considered himself to be a singer by trade, and that he had been an actor strictly for the money.

He nevertheless worked with directors including Godard and Rainer Werner Fassbinder, and his last notable film appearance was in Lars von Trier's Europa in 1991.