By Michael Cairns

The memorable aspect of this map is what it does not show. The map includes an area at the head of the Solway Firth between Carlisle and the England-Scotland border. It is bounded by the A74 road, disused railway line and River Esk, together with a second smaller area to the north of the A6071, west and north west of Smalmstown (squares roughly between eastings 34 – 37 and northings 66 – 68) on this Ordnance Survey One-Inch map of 1971 and is mysteriously devoid of any features other than contour lines and footpaths. It stands out starkly compared with the rest of map where each kilometre square contains roads and buildings as well as a selection of other features such as woodland and marsh, etc.

The answer to the mystery would have been solved in 1971 by driving along the A74, then the main road connecting Carlisle and the M6 from the south with Glasgow. The vehicle’s occupants would have seen a guardhouse and a sign proclaiming Central Ammunition Depot Longtown. The mysterious area contained a large Ministry of Defence ammunition storage site.

The lack of detail was for military security reasons, though the absence of any features on the map made it look conspicuous. Further to this, it had been used for munitions since the First World War when it had formed the eastern end of HM Factory Gretna. Better known as the Gretna Munitions Factory, it stretched over 19 kilometres from Longtown to Dornock, near Annan. Most of the factory site was closed and sold off after the end of the War though the Longtown site and an area at Eastriggs further west were retained for ammunition storage.

Whether leaving the depot off the map produced any security benefits was questionable. The site had been in military use for over 50 years and was clearly visible from the A74 trunk road while the A6071 cut through it.

Munitions are still stored on the site now known as DM (Defence Munitions) Longtown which is managed by DE&S (Defence Equipment & Support), part of the Ministry of Defence, and is clearly shown in detail on all current Ordnance Survey maps. The advent of satellite imagery including non-military availability such as Google Maps negated the justification for omitting the detail. The public footpaths shown on the 1971 map, of course, were not and currently are not accessible to the general public.