War Department property mark WD III. It is located on the base of the old Hargrave's Parade ground denoting it as War Department property.
The obligation to mark the boundary of a site arose under the Military Lands Act of 1892. The act did not specify how the boundaries are to be marked. It only stated that the Secretary of State must “cause the boundaries of the area to which the byelaws apply to be marked, and the byelaws to be published, in such manner as appears to him to be necessary to make them known to all persons in the locality…” (section 17(1)).
Right up to the end of World War II demographic peculiarities of Gibraltar necessarily saw the inclusion of numerous military properties well within civilian residential areas. This necessitated in turn a system to identify, and define the boundaries, of these military properties. Army Barracks, Officers and Married Quarters belonging to the resident infantry battalions stationed in Gibraltar were not marked in this way, possibly because these properties were often clearly demarcated and in constant use by each resident battalion. However, those properties used by the Ordnance Department, the Royal Artillery and even the Navy were much smaller and often embedded deep within civilian areas requiring clear boundary markers to define them as military properties.
The Navy identified their properties either by using the letter N (sometimes with the letter N inverted) or more specifically by using the traditional Royal Navy anchor symbol. In Gibraltar, these symbols appear near the old Royal Naval Hospital, old Admiralty Courthouse, communications centres, stores and former naval properties. Given that the former British Military Hospital was transferred to the Royal Navy in 1963, the tradition of ‘marking’ their properties appears to have been continued well into the second half of the 20th Century.
The Ordnance Department and the Royal Artillery, whose Officers and men were often billeted within the town itself, appear to have used three straight lines (III) to identify their properties. These straight lines probably served as a more visible symbol of the three cannon balls used by the Ordnance Department. Sometimes two lines were used, occasionally just one, and on certain walls a combination of lines and numbers been identified although what exactly these markers represented remains a mystery, particularly as these marks have not been recorded in any OS maps and no legend as to what these marks represented have been found.