There has been a long tradition of amateur military units in the U.K., manned by volunteers. Whilst nothing had ever been seen on the scale represented by the Home Guard in WW2, volunteer units also existed in the Great War which ended on November 11th, 1918.
Here is an image of the Sutton Coldfield Volunteers taken at some time between 1914 and 1918.
Little more than 21 years later, volunteers were again having to offer themselves for service. Some of them were the same men who had been associated directly or indirectly with the Volunteer units of 1914-1918. Perhaps some of these Sutton Coldfield citizens again found themselves in uniform in the summer of 1940, ready to defend their community against a much more imminent threat.