Summarised from report:

The North Lines, which is an expansive ditch and profiled rampart with banquette, connects the Citadel, North Centre Bastion and the Drop Redoubt of the Western Heights, Dover. It was excavated/constructed between 1804 and 1816 to close the gap between the fortifications on the northern side and thereby deny an attacking force access to the weakest positions of the Citadel and the Drop Redoubt. The Lines themselves lacked gun positions, with offensive and flanking firepower being concentrated instead in the Citadel, North Centre Bastion and Drop Redoubt at terre-plein level and in casemates, supplemented by infantry using muskets firing from the Line’s rampart. The North Lines are part of the set of Lines constructed to create an entrenched encampment or fortress on the hilltop to protect a large field force in garrison quarters who could not be accommodated in the Citadel and Drop Redoubt. (1)

<1> Liv Gibbs, 2012, Built Heritage Conservation Framework for Dover Western Heights (Unpublished document). SKE17708.