H.M.Prison, Main Block (A.Wing)

H.M. Prison, Main Block (A Wing) is a 19th-century building featuring robust Italianate detailing, particularly evident in the entrance block. The structure consists of tall north and west wings surrounding an octagonal center, with a diagonally placed entrance block that forms the larger part of a star plan. It has four storeys, constructed from coursed rubble with freestone dressings for the quoins and window surrounds. The roofs are made of corrugated asbestos, featuring oversailing eaves and massive square stacks with cappings.

The south-facing A wing has a total of 15 windows, with 8 on the lower level and 7 above, including three with lowered cills on the top floor to the left. The openings are secured with iron grilles and many retain their original cast iron window frames. The B wing, which runs north, displays similar architectural detailing. The north and west gable ends feature tall round-arched windows. The polygonal center has a brick infill wall on the east face, possibly intended for an unbuilt wing. The south wall has an advanced center with arched voussoir treatment, and a half flying-arch connects the north wing to the center.

The two-storey and basement entrance block faces southwest, with rubble walls and a hipped roof. It has an eaves cornice and a slightly advanced frontispiece that includes a round-arched bipartite window with keyblocks on the first floor. The entrance features a fine cavetto-moulded and rusticated doorpiece linked to a stringcourse, with a blind tympanum and lintel above modern double doors. A flight of steps leads south towards the gatehouse. Modern extensions flank the entrance block and connect to buildings on both sides.

Inside, the interiors predominantly feature painted brickwork, open trussed roofs, ironwork stairs, and cantilevered landings with latticework handrails. Internal openings and doorways have segmental arched heads, while ironwork cell doors and metal grilles are present at the ends of the wings and corridors.