The artillery store is an 1860s building which may have been converted in the 1890s, perhaps to a Side Arms Store (when part of the bombproof shelter became the RA store). It is located on the eastern side of the Detached Bastion with its entrance, contained in a vertical recessed elevation shared with the entrance to the east gallery, reached down four brick steps and protected by steeply ramped flank walls. (location accurate to the nearest 1m based on available information)