The Western Heights of Dover are one of the most impressive fortifications in Britain. They comprise a series of forts, strong points and ditches, designed to protect the country from invasion. They were created in the 18th and 19th centuries to augment the existing defences and protect the key port of Dover from both seaward and landward attack; by the start of the 20th century Dover Western Heights was collectively reputed to be the 'strongest and most elaborate' fortification in the country. The Army finally withdrew from the Heights in 1956–61; they are now a local nature reserve. Introduction First given earthworks in 1779 against the planned invasion that year, the high ground west of Dover, England, now called Dover Western Heights, was properly fortified in 1804 when Lieutenant-Colonel William Twiss was instructed to modernise the existing defences. This was part of a huge programme of fortification in response to Napoleon's planned invasion of the United Kingdom. It followed a sustained period of related work by Twiss on upgrading the fortifications of nearby Dover Castle (1794–1803). The Citadel The Citadel, lying at the western end of the Heights, formed its main defensive point. The Citadel began as a large bastioned fieldwork, constructed in the early 1780s and containing within its fortifications three loopholed guard houses. In 1804 plans were made to rebuild both the 'West and East Redoubts' (i.e. the Citadel and Drop Redoubt) and to link them with earthworks along the length of the Heights. By 1806 the rebuilt Citadel was surrounded by an unrevetted defensive ditch; in the centre was a set of temporary barracks huts (along with the three guardhouses). A well was sunk in 1809, to ensure a permanent supply of water in case of a siege; (a pumphouse was added in 1860). Following a collapse of part of the fortifications in 1807 another application was made for revetting to take place. Nevertheless, at the end of the Napoleonic Wars the Citadel remained unfinished; it was not until the start of the Crimean War in 1853 that work resumed on completing and revetting the ditches. At the same time, some of the existing casemates were adapted to provide barracks accommodation for 500 men. By 1860 the Citadel was entered, via a drawbridge over the ditch, through a gate on the eastern side; a tunnel then led through the rampart into the fort by way of the