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Monument details

Summary

The monument comprises a section of Chatham Lines at Chatham Gun Wharf known as the Barrier Ditch. It represents the early 19th century modification of the most southerly section of the defences on the Gun Wharf, and includes the terminal end adjoining the eastern bank of the River Medway.

Monument Types

• FORTIFICATION (Modern - 1901 AD to 2050 AD)

Full description

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Note: GIS depiction is that of the scheduling which seems to be wider than the monument

The monument comprises a section of Chatham Lines at Chatham Gun Wharf known as the Barrier Ditch. It represents the early 19th century modification of the most southerly section of the defences on the Gun Wharf, and includes the terminal end adjoining the eastern bank of the River Medway. The earlier phase of The Lines at the Gun Wharf appears to have followed a different alignment, located in the area of the New Gun Wharf to the south of the monument. This comprised a ditch with internal rampart crossed by a drawbridge carried road. The gate was defended to its south by a substantial ravelin (a defended outwork) and glacis (a bank sloping down from a defence where attackers were exposed to fire). By 1786 the ravelin was no longer extant although the ditch and rampart continued on the same line but this was to be replaced in the early 19th century by a new alignment to the north. The monument includes the intersection of the primary and secondary phases of The Lines.

Historical sources indicate that the Gun Wharf section of the modified alignment was completed and the ditch reveted in brick by about 1805. The ditch ran north-south for approximately 80 feet (24.4m) immediately adjoining the river before making a right-angled turn to the east. Here a counterscarp gallery of three casemates was located to provide lines of fire along the ditch in both directions. The ditch then continued in an easterly direction for a further 300 feet (91.2m) where it was crossed by a drawbridge carrying the Chatham road from the south into the military zone. A guardhouse, known as the Lower Guard House and which partly survives, had the dual role of protecting this external gate as well as regulating traffic onto the Gun Wharf. A rampart was located on the inner face of the ditch with a small square bastion (now lost) located at its terminal end. The bastion is likely to have been a later addition to the early 19th century defences. A cartographic source shows it as a small rectangular structure with a banquette (an infantry firing step) and parapet on all sides, approached by a pair of steps.

The western two thirds of the monument do not survive above ground but are preserved under public open space. The western angled termination and bastion had been lost by 1932 by which time the lower end of the Barrier Ditch had been infilled and the re-entrant in the river frontage removed by the wharf being extended across the corner. Observations during late 20th century river wall repairs and landscaping confirmed that the Barrier Ditch survived intact in this area but had been backfilled. The eastern third of the monument is partially located under Riverside 1, a building constructed within the Barrier Ditch at some point between 1900 and 1932.

The basement of Riverside 1 has been constructed using the scarp and counterscarp of the Barrier Ditch to form its north and south external walls. The battered ditch sides are visible internally surviving to a maximum height of 2.3m. The building's east wall is formed by the western elevation of the 1876 fixed bridge carrying Dock Road into the militarised zone. This replaced the earlier drawbridge. The two bridge arches (now bricked-up) are visible in the basement. The terminal end of an east-west stretch of rails is located in the floor of the north east basement room (the current boiler house). The gauge of the rails is 18 inches (0.46m) wide. Although only a short stretch
(1.45m) is visible, the rails survive under the remaining length of Riverside 1 to the west and have also been deliberately preserved under the full width of the adjacent car park to the west.

A brick reveted banquette survives to the north of and immediately adjoining Riverside 1. The parapet stands approximately 4m above the present ground level. Behind and to its north is the infantry firing step, and below this a sentry path. The rampart survives for a length of approximately 28m east-west and would have originally terminated at its eastern end, adjacent to the western elevation of the Lower Guardhouse. This relationship has been interrupted by the insertion of a modern porch. The surviving elements of the Lower Guardhouse comprise ground and basement levels surmounted by a later 19th century first floor. At ground level the north elevation exhibits two contiguous arched openings, the most westerly of which has been altered with the insertion of a later window and door. This section is blocked and inaccessible. To the east is a north-south barrel vaulted room. The south wall contains a blocked fireplace flanked by two arched niches. In the south east corner is an arched recess leading to a blocked square-headed door. This is the entrance to a short tunnel which runs under Dock Road to Fort Amherst to the east. The basement level is accessed by an arched entrance in the north elevation, located under the present ramped road onto the Gun Wharf. This is also a brick built north-south barrel vaulted room with a rammed earth floor. It comprises 5 unequal bays each separated by a brick arch. Two brick pillars support the roof in bay 4 and are presumed to relate to the later addition of the first floor. The room is approximately 15m in length north-south and extends beneath the Gun Wharf access road and barrel vaulted room above. Its south elevation is part of the scarp of the Barrier Ditch and contains a blocked casemate. This would have provided covering fire for both drawbridge and ditch.

All modern ground and road surfaces, telegraph poles and modern street furniture are excluded from the scheduling, although the ground beneath them is included. All existing services and their trenches are excluded from the scheduling although the ground around and beneath them is included. The first floor of the Lower Guard House is excluded including the modern floor, although the ceiling of the ground floor is included. The 20th century structure of Riverside 1 is excluded from the scheduling although the historic fabric which forms the north, east and west elevations of the basement is included. The floor of the north east room immediately adjoining Dock Road (the current boiler room) is included as is the ground beneath the modern basement floor to the south and west, although the modern floor itself is excluded. The rampart to the north of Riverside 1 is included. The late 19th century former ordnance building to the north-west of Riverside 1, known as the Blacksmith's or Machine Shop, is excluded, although the ground beneath its south end is included.

ASSESSMENT OF IMPORTANCE
The Chatham Lines were first constructed in 1755 as a defensive fortification to protect the landward side of Chatham Dockyard and the subsequently associated barracks. The pre-existing civilian settlement of Brompton was incorporated into the militarised zone.

A Board of Ordnance report of 1708 discussed the strengthening of fortifications at a number of sites, including Chatham, and was followed by a land purchase and survey in the early 18th century. The 1755 construction was probably a response to an invasion threat during the Seven Years War between Britain and France (1756-1763), with Chatham Dockyard a potential target for French attack. Tensions between the two countries had been building specifically in relation to their dealings with the colonies. Britain declared war in May 1756 and France retaliated by seizing British colonial bases. Conflict also took place in the Mediterranean and Northern Europe.

Designed by Captain John Peter Desmartez and constructed by military personnel under the direction of Hugh Debbieg, The Lines comprised an earth rampart and unrevetted ditch enhanced by bastions. The continuous circuit ran from the north end of the Dockyard (the `Ligonier Line') to the Gun Wharf to the south (`Cumberland Line'), adjoining the east bank of the River Medway at either end. The ditch was 12.4 feet (3.7m) wide at the base, battered to a maximum width of 24 feet (7.3m). From the base of the ditch to the top of the internal rampart was a maximum of 15 feet (4.5m). A series of horizontal stakes (known as `fraises') were inserted on the scarp at a height of 7 feet (2.1m) from the base of the ditch to prevent the enemy scaling the defences. The glacis was approximately 19 feet (5.7m) wide, measured from the edge of the ditch. The internal rampart comprised a banquette (an infantry firing step) and was designed in two different forms, one with an additional sentry path behind the banquette. Three gates (one a sally port), approached by drawbridges and protected by gatehouses, allowed access to the enclosed garrison area.

The Lines were intended to perform both a defensive and offensive function. Exploiting advantages in the local topography and deliberately enclosing substantial areas of open ground, the design was a deliberate response to the capabilities of contemporary artillery. The open ground within The Lines formed a protective zone to absorb enemy fire directed at the Dockyard and barracks, as well as providing essential areas for troop encampments and exercises. The Lines also served as a physical barrier, shielding the garrison from enemy gaze prior to any counter attack. The garrison could then advance through the defences to engage the enemy in the open area of the field of fire or indeed further into Kent.

The Lines were subsequently extended, realigned in places and reinforced in the late 18th century (at the time of the American War of Independence of 1775-1783 when France allied herself with the rebellious North American colonists). A third construction phase, a substantial rebuild in the early 19th century, was again in response to a perceived threat from France in the build up to and during the Napoleonic Wars (1803-1815). Modifications in the 1770s and 1780s strengthened both ends of The Lines, with Amherst Redoubt constructed at the south end and Townsend Redoubt at the north. Amherst Redoubt, in conjunction with Prince William's Redoubt, Belvedere Battery, Spur Battery and the `Couvre Port' (a covered gate), developed in the 1790s into the Fort Amherst complex, a rare survival of a British Napoleonic fort in its original form. The Lines were extended northwards to St Mary's Creek and this new section was known as the `Lower Lines'. Outlying forts, such as Forts Clarence and Pitt constructed to control the roads and approaches to Rochester Bridge, further enhanced the defences. The ditches and ramparts were also revetted in brick as the unrevetted defences had proven unstable. This was completed by 1805. The Lines were never tested and were declared obsolete by the 1860 Royal Commission, which concluded that the defences were redundant, given changes in military technology. A series of new forts were therefore constructed to protect the dockyard (the same approach also being taken to the defence of the dockyards at Portsmouth and Plymouth). At Chatham seven were constructed in an arc about one and a half miles from the dockyard. (Forts Borstal, Bridgewoods, Horsted, Luton, Darland and two infantry redoubts at Twydall). However, The Lines continued to play a role as a control point and demarcation line between the military garrison and surrounding civilian settlements. Elements found a new use, such as the internal open space which became pleasure gardens for the officers. The Lines also continued to perform a military training function and were used to test defensive and offensive techniques and strategy prior to foreign campaigns.

The Lines were reused both during the First and Second World Wars. Between 1914-18 they functioned as a training ground for trench warfare and mining. During World War II they were heavily re-fortified, with the ditch serving as an anti-tank obstacle in a line of Medway defences. Air raid shelters, anti-aircraft guns, an emergency reservoir and at least one pillbox and spigot mortar were added at this time. The Lines were also used for Home Guard training.

The section of The Lines at Chatham Gun Wharf is a critical component of the early 19th century defences and represents the southern terminal of the circuit. The monument survives in good condition and includes archaeological evidence of the earlier 1750s defence and of one of the defended gateways into the militarised zone. The relationship of The Lines and the Gun Wharf is also of considerable importance to our understanding of Chatham's military function.

English Heritage, Register of Scheduled Monuments (Scheduling record). SKE16191.

Sources and further reading

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