The ditch surrounding the Detached Bastion is generally 12.0m wide, part of it follows the line of the original linear fieldwork, dating probably from the American war of the 1770’s and 80’s, though it has been much altered in subsequent periods of modernisation/restoration. The scarp revetment was added during the 1860’s phase of works on the fort. It 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. 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. (location accurate to the nearest 1m based on available information)