Guard house, disused. 1788, built by Isaac Ashton, possibly to designs of James Wyatt.
Yellow and red stock brick with limestone ashlar, ridge stacks and hipped slate roof. Single-depth plan with central archway. Two storeys; 3-bay range. A tetrastyle Doric portico 1 bay deep with a modillion cornice, to a similarly-sized flagged recess, a central doorway with double 6-light doors with raised panels, and smaller ones to the guard houses each side. Segmental-arched ground-floor tripartite 6/6-pane sashes, and gauged brick flat heads to first-floor 6/6-pane sashes with ashlar cill band. Rear has projecting wings each side of the central entrance.
INTERIOR: has cast-iron posts.
HISTORY: Used by the Army when it provided guards for the site, and an important part of the C18 Arsenal.