This film, the centrepiece of the Robert Siodmak season at the BFI, is on an extended run until May 27. You can find all the details of the screenings here.
An electrifying variation on the theme of a hoodlum (Conte) and a cop (Mature) who knew one another as kids, it opens with the former seriously wounded in hospital but determined to escape the police watching over him; he needs to clear the name of his fiancée, who’s suspected of a jewel robbery. While Conte, all insolent, menacing charm, is especially magnificent, and Mature invests the detective’s pursuit with unsettling hints of obsession, the movie fields a glorious gallery of shady figures, from a lawyer oozing corruption to a memorably sadistic masseuse. The steely realism is enhanced by flourishes of noir stylisation. A classic awaiting rediscovery.
There's also a terrific review by critic David Jenkins in Little White Lies magazine which you can read here.
Here (and above) is the trailer.