I've just heard about one film I've never seen, "Les diaboliques" (1955), by French director Henri-Georges Clouzot. It seems that in this film there is a private detective who is very much like Columbo, so much that it's been suggested that he must have been a major influence on Levinson and Link to create their character.
Has anybody heard about this before? Have you seen the film? In what aspects does that inspector resemble Columbo?