The Drop Redoubt is at the eastern-most end of the North Lines, that is the system of dry ditches extending from the Redoubt westwards towards Folkestone for the entire length of the defences. During the invasion fever of 1804 it was decided by the Inspector General of Fortifications, Lieutenant-General Robert Morse, that there should be a Citadel at the western end of the west hill, this to remain largely a fieldwork as laid down 20 years previously, a polygonal fort at the eastern end, at the Drop, a powerful detached work midway, the three linked by a strong defensive ditch. These turned into the Citadel, Drop Redoubt and North Centre Bastion respectively.
The first building programme on the Drop Redoubt ran between 1804 and 1810. There was a second building program on the Heights during the 1850s and 1860s due to yet another invasion scare by yet another Napoleon. A Royal Commission was set up to look into the defences of the United Kingdom and recommend improvements thereto.
It was then that the modern Drop Redoubt that we know today was finished; The four caponiers were added, as were bombproof officers quarters, the ditch running from the redoubt to the cliff edge, and the main magazine was strengthened. The four caponniers were added to enable enfilading fire along each ditch. These were not just stuck on the corners of the redoubt, but knitted into the brickwork along with corresponding bulges in the counterscarp walls. The barracks provided accommodation for 4 officers and 90 men.
The drop redoubt was decommissioned in the 1950s when Coast Defence officially finished and for many years remained in a state of decay. Several attempts to carry out conservation were made over the years but all ended prematurely due to excessive vandal activity. Even the spotlights which were installed in 1994 to illuminate the redoubt at night to match the Castles flood lights had been either smashed or stolen.
The latest programme of conservation currently being carried out by English Heritage has been going on for three years now and so far has been reasonably vandal-proof thanks to the vigilance of the workmen and EH. This is not to ignore the copious amounts of tools that have been stolen from on-site lock-ups and the odd attempted break-in.
Drop Redoubt Caponier no. 4 following conservation work (October 1998)