Blocks 21 and 23 (HQ Block and Rear Block)

Blocks 21 and 23, known as the HQ Block and Rear Block, are former Cavalry Barracks built in the 1840s. The building features a long two-storey range with seventeen 12-pane sash windows, along with some smaller later windows. At the center, there is a square stone clock tower topped with a weather vane, and the roof is hipped and covered with slate. Rectangular stone chimneys are present as well. The entrance doorways are flanked by squared stone pilasters in the 3rd, central, and 15th bays, and there are decorative bands at the eaves above the first floor and a plinth at the base.

At the rear, a lower two-storey range connects to the main building via a later corridor. This section also has a stone structure with a slate roof and stone chimneys. The walls are made of squared rubble with ashlar dressings, featuring bands at the first floor sill level and above the ground floor windows. There have been some alterations to the openings, but the majority still retain the 12-pane horned sash windows.