The success of this movie, in spite of its controversial themes, encouraged Janet Green to write Victim (1961), and Basil Dearden to direct it.
Paul Slade's car is a 1949 Jaguar XK120 open two-seater. From 1948 to 1954, 7,606 were built in both left and right-hand drive. In excellent condition, this car could bring in well over $270,000 at auction in 2024.
The detectives are driven around in a 1957 Wolsely 6/90 Series III. This same car can be seen in Neues vom Hexer (1965), Tres crímenes y un asesino (1964), The Sanctuary (1960), and Das Geheimnis der gelben Narzissen (1961).
Debut screenwriting credit for Lukas Heller. He is credited only with "additional dialogue," his name in much smaller print that that of screenwriter Janet Green. Heller claimed many years later that Green's screenplay had been unsatisfactory - that it had been well-intentioned but unwittingly condescending to its black characters and inaccurate in its portrait of black lives in 1950s London - and that he had done extensive rewriting at the behest of director Basil Dearden, who had employed him in a similar way (without credit) on some later films.