The Somerset Position is now generally know as Scaur Hill. This defensive position was chosen by Colonel Jervois in his report of 1865 to protect the Royal Navy Dockyard from land attack from the South West. At this point, Somerset Island is only 500 metres wide and Colonel Jervois recommended a continuous dry ditch with a rampart. A redoubt to be positioned in the centre.
It would appear that work had commenced on the defence line by 1878 based on a plan entitled Scaur Hill Position of 1875. It is believed that as the built, the position mounted no fixed gun emplacements. At this time there was a dry ditch across the whole of Somerset Island, with a rampart on the North side. The redoubt included a caponier covering the entrance, and two scarp and two counterscarp galleries. There were also two musketry galleries across the foot of the ditch, covering the flank of the two scarp galleries.
On the 27th April 1983 authority was given to build the two 64-pdr gun emplacements. The cost of these works was £7,925. The date of completion of this work is now known. Each of the gun pits was armed with a 64-pdr RML gun on a Moncrief Disappearing Carriage.