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. 7,606 were built in both left- and right-hand drive from 1948 to 1954. In excellent condition, this car could bring in well over $100,000 at auction in 2020.

Dirk Bogarde was asked to play Learoyd.

The detectives are driven around in a 1957 Wolsely 6/90 Series III. This same car can be seen in Again the Ringer (1965), Murder Most Foul (1964), Danger Man: The Sanctuary (1960), and The Devil's Daffodil (1961).

Feature film debut of Fenella Fielding.

The barman at the Tulip club tries to charge Superintendent Hazard 10 shillings for three bottles of beer. Allowing for inflation that would be £11.72 or about $15.29 at exchange rates in February 2020.