In April 1860 that the Defence Committee considered the construction of casemated barracks in the South Lines, to provide bombproof accommodation for 400 men. The new barracks were a three storey casemated range forming a truncated L-shape, abutting the gun rooms of the extended south lines casemates. These gun rooms continued to cover the south lines ditch while the extension formed a caponier which projected into the north eastern extension of the South Lines ditch, thereby providing flanking fire along the barracks, whose south east elevation formed the escarp of the ditch. They were situated around the sides and ends of a long rectangular gorge, in this case effectively a protected courtyard, created by cutting deeply into the chalk rock of the hillside. (location accurate to the nearest 1m based on available information)