The film was based on a radio series that featured Jon Pertwee and Dennis Price among the main cast. According to Pertwee, film producer Herbert Wilcox refused to hire Price for the film spin-off because Price was "gay". Pertwee protested on Price's behalf, and Wilcox fired Pertwee as well.
Leslie Phillips was the only cast member from the BBC Radio series to reprise his role in the film. However Richard Caldicot (the radio show's Captain Povey) makes a cameo appearance in a different role.
Although the film has an almost entirely different cast, many of the character names are retained from the radio show.
The fictional HMS Trumpton was the minesweeper HMS Reedham. Also seen is the corvette HMS Portchester Castle.
Boonsey is a fictional Channel Island based loosely on Guernsey.