 This dictated the placement of one Heavy Anti Aircraft Gun Station (A Troop) at the western end of the valley at South Bowenfels and the other Heavy Anti Aircraft Gun Station (B Troop) at the eastern end of the valley on the heights of Scenic Hill overlooking the Vale of Clwydd.A third detachment was to be mounted on the roof of the Small Arms Factory using a Lewis Machine Gun for the close defence of the factory and to provide protection against strafing fighters and from dive bombers.Work began on the stations immediately and workmen from the Water Conservation and Irrigation Commission poured the concrete floors of the emplacements prior to 22 December 1941.