H M Prison Dartmoor: Inner Gateway, Former Guard's Rooms, Carriage Way and Perimeter Wall

An enclosed gateway with former guards' rooms built in 1878 to designs by the Prison Commission, set against the prison perimeter wall first built in 1809 to designs by Daniel Asher Alexander, raised in 1812, and with later repairs and alterations.

The gateway is constructed in granite ashlar blocks with rustication to the two gates. The guards' buildings have hipped slate-covered roofs. The courtyard was originally open but since the 1990s has been covered in curved corrugated plastic sheets resting on steel beams. The perimeter prison wall is built in granite stone rubble with curved copings.

The gateway, enclosed by a wall, has a rectangular plan. Two gates aligned with the outer prison gate situated to the south-west (Grade II) give access to a central rectangular-shaped courtyard with guard accommodation to either side and a small gate keeper's lodge to the left-hand side of the inner gate. The courtyard also contains three small, freestanding flat-roofed buildings added in the late twentieth century, two flanking the outer gate and a larger one flanking the inner gate.

The gateway is built against the prison's early nineteenth-century inner wall, which links up with the prison's perimeter wall, thus forming a horse-shoe shaped enclosure accommodating the radial layout of the prison buildings within it.

The outer gate to the inner gateway is constructed in rusticated granite ashlar blocks forming a round arch with a dropped keystone. The plain entablature above it is topped with a later-added flat-topped bellcote. The gate, which has full-height timber doors, is flanked to either side by rusticated pilasters set against the wall which encloses the inner gateway complex. This is constructed in granite stone rubble with granite stone rounded coping. Some sections of the returns have been raised.

The courtyard is laid with tarmac but contains a granite cobbled carriageway lined with granite flagstones starting from the main gate to the prison, covering a total length of approximately 35 metres. Steps to either side of the courtyard each lead to a colonnade of three centred arches resting on square columns and the guards' rooms behind. The inside of both gates is now no longer visible due to the late twentieth-century roof covering over the courtyard, except for the pediment of the inner gate, which can just be seen from a distance, outside the prison, and shows the inscription 'VR AD 1878'. The other side of this gate, facing the inside of the prison, has rusticated jambs and voussoirs and is topped with a plain pediment. Its late twentieth-century metal gates replace earlier cast iron gates.

The granite stone rubble perimeter wall to the prison extends from either side of this gate and rises to a height of approximately 6 metres. Parts of the outside of the wall are supported by later-added full-height buttresses set at regular intervals. Approximately 50 metres south-east of the inner gateway the perimeter wall has another gate, inserted in the late twentieth century, allowing access to a contractor's compound outside the prison wall. In the south part of the wall, adjacent to the current B wing, is a blocked gateway formerly leading to the soldiers' barracks outside the prison, allowing them more direct access to the former market place where they could trade with the prisoners of war. The lintel to the blocked gateway bears an inscription reading 'HENRI PRISONNIER 1813 JOURNE FRANCAIS'. At the north end, opposite the French Prisoners of War Cemetery outside the prison, is another large blocked opening in the wall. This gate, formerly allowing prisoners access to the prison farm and quarry, was closed off in 1963 following prisoners attempting an escape by ramming an oil tanker through it.

The interiors of the former guards' rooms could not be inspected as of 2015.