The threat of a German invasion or raid was taken very seriously and throughout the war considerable forces were retained in the UK for Home Defence. In addition to coastal defences of various kinds, a number of what came to be called 'stop lines' in the next war, were dug covering the approaches to London. Much of this digging was done by men of the Volunteers in their spare time, and members of the United Arts Volunteer Rifles can be seen in IWM photograph Q23549 at work at Woldingham (near Caterham) Surrey, in 1916. The trench was part of 'London's outer defences', a project aimed at defending the capital with complete trench lines, very roughly between twenty and thirty miles north and south from the centre of the city. Work on it extended into the following year.
The United Arts Volunteer Rifles was the Volunteer regiment that in 1917 absorbed the London Pharmacists Volunteers described by Ray Westlake in ST/36, p27. The caption to this photograph says, 'Fred Wright with the pick'