This film was originally produced as a Military Training film. It was designed not only to make British servicemen aware of the need for security and to keep secrets, but to give the general public the same awareness as well.
The film puts good emphasis on just how easy it would have been to become careless and not realise who you were talking to. It showed that even the smallest and most insignificant piece of information could be of use to a Foreign Power - all part of a large jigsaw puzzle.
However, to anyone else this film comes over as a very good wartime spy thriller.
Mervyn Johns plays the part of a very skilful fifth columnist working for German Intelligence. His performance is so good that you would almost mistake him for being the hero rather than the villain. You could go on believing this until, at the end of the film, you come realise what damage his duplicitous and despicable deeds have done.
At the very beginning of the film, his accomplice is caught by the British, along with the rest of the network making up his organisation. However, himself being older and wilier, survives right up till the very end. The last scene shows how he manages to carry on with his sneaky and contemptible work, continuing to remind the audience that you cannot be too careful about who you are talking to, or sitting next to.
It was nice to see many of the celebrated actors of the day appearing in cameo roles. Names such as Jack Hawkins, Nova Pilbeam, Thora Hird and, the ever reliable, Naunton Wayne and Basil Radford, would have given the film the right amount of box office appeal.
Incidentally, the "goof" that is reported as a "geographical error" on IMDB was probably deliberate. As, with many films about England that were made during the Second World War, it was sometimes necessary to give false geographical locations, should a recording of the film be seen by an agent of a Foreign Power. With this in mind, it should be noted that, in the case of this film, the town of Westport on the Northern Coast of England, is deceptively fictitious for security reasons.
