This film was originally intended as a Ealing short to put across the principles of economic warfare. Sir Michael Balcon the head of Ealing Studios was to put extra finance into it, thus building it up into a feature. Will Hay appears with an all-star cast in a cameo role as a skipper of a British merchant ship who goes on to describe to his mate, Bernard Miles the meaning of "Navy Certificates" and the role that they will play in the war.

Whilst describing the navicert system we see Hay man the ships guns and shoot down a enemy aircraft all the time still going on about the virtues of navicert. The writer Angus McPhail who had earlier collaborated on The Ghost of St. Michael's with John Dighton unfortunately fails to find anything funny for Will Hay to say and one can imagine people arriving at the cinema with great anticipation, looking forward to another Will Hay film, only to find him  in a humourless role.

The film with it's uneasy mix of propaganda as entertainment sits a little uneasy, but it should be considered as part of our social history of that time.