At intervals around the coast of Wales systems of First World War (1914-18) practice trenches survive as grim reminders of the training given to fresh conscripts before their transport to the Western Front. The surviving earthworks at Penally show many standard characteristics clearly laid out in manuals and guidelines of the day. Trenches were built in parallel lines, usually three, linked by communications trenches. Two frontline trenches were supported by a third reserve one, although, as artillery power strengthened and increased in range, changes were made during the war to the standard layout. The saw-toothed plan prevented shell and bomb blasts travelling along the trench. This also made it impossible to see more than ten metres along a trench, maintaining the security of the system even if the enemy infiltrated one particular part. The Penally system measures 260m E-W by 100m and consists of two lines of firing trenches, linked and extended by communication trenches or saps, facing north and apparently based on an east-west running field boundary feature. In places the system has been dug through bedrock.
Source: Driver, T. 2007, Pembrokeshire: Historic Landscapes from the Air, RCAHMW, pages 260-1.
RCAHMW, 06 November 2008.