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H M Prison Dartmoor: Reservoir, with retaining wall, conduit head and nearby tank

A Grade II Listed Building in Princetown, Devon

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Latitude: 50.5491 / 50°32'56"N

Longitude: -3.9986 / 3°59'54"W

OS Eastings: 258501

OS Northings: 74053

OS Grid: SX585740

Mapcode National: GBR Q2.VYGG

Mapcode Global: FRA 27JM.01L

Plus Code: 9C2RG2X2+JH

Entry Name: H M Prison Dartmoor: Reservoir, with retaining wall, conduit head and nearby tank

Listing Date: 28 October 1987

Last Amended: 12 February 2016

Grade: II

Source: Historic England

Source ID: 1326423

English Heritage Legacy ID: 92800

Location: Dartmoor Forest, West Devon, Devon, PL20

County: Devon

District: West Devon

Civil Parish: Dartmoor Forest

Built-Up Area: Princetown

Traditional County: Devon

Lieutenancy Area (Ceremonial County): Devon

Tagged with: Architectural structure

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Reservoir at Dartmoor Prison, constructed in 1806-9 as part of the original design by Daniel Alexander.


Reservoir, constructed circa 1806-9. Restored in 2013.

MATERIALS: granite ashlar.

DESCRIPTION: the reservoir is a long, slightly irregular elliptical feature, sited to the west of the prison, on a north-south alignment. The reservoir is lined with granite ashlar, in blocks of unequal size. To the east of the reservoir is a circular unroofed conduit head with a central doorway facing the prison. This structure is of regularly-sized and coursed granite ashlar, with a tall plinth and a bull-nosed stringcourse beneath the plinth.

SUBSIDIARY FEATURES: a retaining wall supports the raised ground in which the reservoir and conduit head are set; this is of granite rubble with a capping of rock-faced granite with drafted margins, and with piers having pyramidal caps - the dressed granite of the capping and piers probably indicates a later-C19 phase of work.

Above the reservoir, a short distance to the north-west, is a circular tank lined with coursed granite, with dressed granite to the rim. This feature, is fed by a spring, appears on the 1884 Ordnance Survey, pre-dating the later covered reservoir to which it is now adjacent.


Dartmoor Prison was built by the Admiralty in 1806-9 on land leased from the Duchy of Cornwall, to receive prisoners of war. During the Napoleonic Wars of 1803-15 there were 47 prisoner of war hulks moored at Chatham, Portsmouth and Plymouth, and pressure on Plymouth was increased when prisoner of war prisons at Norman Cross, Northamptonshire and Stapleton near Bristol became full. The London architect Daniel Asher Alexander (1768-1846), was employed to design Dartmoor Prison.

The first inmates were received in May 1809, and by June that year the prison housed 5000 prisoners of war. As described in Risdon’s Survey of Devon (1811), and illustrated by two views by Samuel Prout (1809 and 1811), by a drawing in Ackermann’s Repository of 1810, and by a survey drawing of the prison of 1847, Dartmoor Prison originally consisted of five blocks laid out in a radial arrangement around a central market place, in total covering c12ha and surrounded by a double, circular perimeter wall. Internal walls divided the prison into a number of sections. In the central market place prisoners could trade with outside traders. The western part of the prison included an Infirmary and a separate Petty Officer’s Prison. The main entrance of the prison was flanked to the right by the Governor’s House and to the left by the Surgeon’s House. In 1812, following the outbreak of the trade wars with America, two blocks were added to house prisoners, and the Petty Officer’s block was converted into a barrack to supplement the large barracks complex south of the prison. The prison closed in 1816. Despite the opening of a railway from Plymouth to Princetown in 1827, the area saw little economic development following the prison closure.

In 1850 the prison re-opened as a civic prison to address the contraction in the transportation of prisoners to Australia; alterations were made to the convict accommodation, and by 1851 there was room for 1030 inmates. During the 1860s, 1870s and 1880s a number of alterations were made to the prison by the architect Sir Edmund du Cane (1830-1903), appointed Director of Convicts and Inspector of Military Prisons in 1863, and Surveyor-General of Prisons, Chairman of the Board of Convict Prisons and Inspector-General of Military Prisons in 1869. Further rebuilding of the prison took place during the first quarter of the C20, with four new wings built between 1901 and 1915. A detailed description of Dartmoor Prison during this period was published in 1909-10 by RG Alford (Notes on the buildings of English Prisons, vol. 2, pp75-87).

During the First World War Dartmoor Prison housed around 1000 conscientious objectors, who mainly undertook farm labour or worked in quarries on the Moor.

Dartmoor Prison has seen much change in the course of the C20 and early C21. Major prison riots which took place in prisons across the country including Dartmoor in 1990, led to an extensive refurbishment programme to improve the prison’s security. Despite the degree of rebuilding which Dartmoor has undergone over more than two hundred years, the radial plan established by the original design has survived.

The reservoir located to the west of the prison gates was constructed during the first building phase of 1806-9, and forms an important part of the original system for the supply and circulation of water. In order to provide this, water was carried from higher ground to the west along a leat four miles in length and passed into the reservoir. From the reservoir the water passed under the road and into an open conduit that ran around the site and drained out at the east side of the site; it was then carried in a leat to land at Tor Royal, to the south-west of the prison. The freshest water was therefore supplied to the Infirmary and the Petty Officer’s prison to the west of the site. Water moved both clockwise and anti-clockwise around the prison and passed beneath small privy blocks attached to the outer ends of each wing, a system of sanitation akin to medieval monastic reredorters. A bathing pool, located roughly on the site of the present E Wing, features in the view of 1810, but was apparently removed when new internal walls were built in 1812. In 1900 the sewerage aqueduct was constructed, to carry waste away from the prison across the Blackabrook River to new sewage works.

The reservoir was restored in 2013, with prisoners taking part in the restoration work, and is now maintained for wildlife.

Reasons for Listing

The reservoir at Dartmoor Prison, constructed in 1806-9 as part of the original design by Daniel Alexander, is listed at Grade II for the following principal reasons:
* Historic interest: an integral part of the original Dartmoor Prison complex of 1806-9, the reservoir stands between the moor from which water was drawn, and the prison, illustrating a key element of the site’s historic infrastructure;
* Design interest: the circular conduit head, seen on early depictions of the prison, is a small but striking feature, which with the granite-lined basin and retaining walls survives as a good example of a small reservoir of this date;
* Group value: the reservoir forms part of an important and relatively complete group of listed prison buildings, both within and outside the prison walls; there is a particularly direct link with the drinking fountain set in the wall by the outer gateway, and with the sewerage aqueduct to the east of the complex.

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