If the invader comes these chaps will know what to do! Watch as the men of the Home Guard plan how to defend the fictional town of Onebridge and its surrounding countryside.

This film, sadly incomplete, is a dramatised account of how the fictional town of Onebridge is defended by the local Home Guard. It shows members of a committee and the roles they play in civil defence interspersed with scenes showing Home Guard exercises and anti-invasion preparations. Weapons training is shown as well as the construction of fortifications and the use of camouflage techniques. A visiting General causes some hilarity amongst the ranks.

The scenes depicted in this film might seem quaint today but, the often patrician tone notwithstanding, were deadly serious at the time. After that Fall of France there was a realistic expectation that the Nazis would commence 'Operation Sealion', the invasion of the British Isles, during the late summer and autumn of 1940. The ultimate failure of the Luftwaffe to achieve total air superiority over Britain's skies meant that the plan to invade was postponed - since the destruction of the Royal Air Force was a key prerequisite to any invasion attempt by the Wehrmacht and the Kriegsmarine.