Summarised from report:

Detached bastion has a trapezoidal plan, with a ditch defining the defensible ‘island’ of the bastion. The ditch is generally 12.0m wide, except on the east, where it was reduced to only 9.0m in the rebuilding of 1867. Part of the ditch follows the line of the original linear fieldwork, dating probably from the American war of the 1770’s and 80’s which was aligned east to west along the north face of the Heights, outside and parallel to the later North Lines. This was however remodelled and adapted during the Napoleonic (c1804-1810) phase of works and then again during the 1860’s completion and modernisation of the fortress, to resemble the ditch as it is today. Its line is usually straight except on the north-west where it adopts a prominent arc around the north-west caponier. The scarp revetment is in stock brick laid to English bond and is vertical except on the east, where it is battered. The counterscarp revetment utilises split and faced flintwork, with periodic string courses in red brick and there is a portion along the west side of the counterscarp which is unrevetted chalk except for the top 2-3m, which is in flint.

The cross ditch, also 12.0m wide, has a change of level down to the North Lines at its eastern end. The change is marked by an angled brick revetment in English bond, some 2.92m high. This served as an obstacle to an attacker, who, having negotiated it would have been faced by the south caponier at the other end of the ditch. For the most part, construction of the bastion ditch involved cutting down into chalk bedrock. The glaçis is between 7m high on the north and 10.5m on the east and was designed to absorb the impact of incoming bombardment, and its slope very steep to render infantry assault arduous. There is a low counterscarp bank between the lip of the counterscarp and the glaçis, slighter on the east and north sides, at 0.6m high and larger on the west side, where it broadens to 19m wide and 1.4m high. This probably served as further protection for the ditch revetments. (1)

A plan dating to 1810 shows the Detached bastion as it was originally constructed and before any improvements were made under the 1860's scheme of works, (2) while another dating to 1862 shows the bastion after the major improvements have been made and includes details of the ditches, gun emplacements and some of the interior structures. (3)

Office of Works, 1862, Plan showing the improvements to the defences for Dover at the North Centre Bastion at the Western Heights (Plan). SKE51590.

<1> RCHME, 2001, The Western Heights, Dover, Kent. Report No 7: North Centre and Detached Bastions: 19th-century fortifications (Unpublished document). SKE17503.

<2> E B Metcalf, Royal Military Surveyor and Draughtsman, 1810, Kent: Dover. Map showing fortifications. At the Western Heights
Kent: Dover. Map showing fortifications. (Map). SKE51587.