The coin-tossing game (known as "two-up") was notorious for deceiving naive players. Such people assume the three outcomes, two heads, two tails, and a head-and-a-tail, to have equal likelihood, 33%. In fact a head-and-a-tail has 50% probability, and the others have 25%.
This was the last Hammer Film of Stanley Baker as his services could no longer be afforded.
The film was considered quite violent for the times. This was courtesy of scenes showing a woman being coshed to death, a police officer being kicked in the ribs after being shot and a woman being shot in the back.
The film is shot "in Hammerscope".
In the director's commentary, Val Guest said he was inspired by American TV-show Dragnet. His co-commentator (interviewer) brought up similarities from John Huston's classic film noir The Asphalt Jungle, which Guest said wasn't an inspiration.