Henley Fort: a London mobilisation centre


Heritage Category:
Scheduled Monument
List Entry Number:
Date first listed:
Date of most recent amendment:


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The building or site itself may lie within the boundary of more than one authority.

Guildford (District Authority)
National Grid Reference:
SU 98192 48837

Reasons for Designation

The 15 London mobilisation centres, constructed during the 1890s, formed part of a comprehensive military scheme known as the London Defence Positions, drawn up in 1888 to protect the capital in the event of enemy invasion. The scheme was a response to the rapid progress made in warship production by France and Russia during the early 1880s, which had led to official doubts about the Royal Navy's defence capability. Essentially a contingency plan, it provided for the establishment of a 72 mile long, entrenched stop-line divided into ten tactical sectors and supported by artillery batteries and redoubts. The planned stop-line ran from the southern edge of the Surrey and Kent Downs, up the western side of the Darenth Valley to the Thames, and then north westwards through Essex from Tilbury Fort to Epping. Although the stop-line and main defence positions were not to be established until an invasion was imminent, it was thought prudent to build a series of mobilisation centres, 13 on new sites, along the projected course, either for artillery deployment or where troops could assemble and collect tools and supplies. By 1905, official confidence in the Royal Navy had been restored, and the now obsolete mobilisation centres were abandoned and gradually sold off. No two mobilisation centres are exactly alike, and a broad distinction can be drawn between the four centres purpose built for artillery deployment, and eight which functioned as infantry positions. However, in general terms there are close similarities: each, for example, was typically enclosed by a rampart, ditch and spiked fence, containing a partly earth-sheltered, reinforced concrete and brick built magazine and stores. Beyond the main compound were associated buildings of a standard type, including a brick caretakers lodge and a large, barn-like tool store. Most mobilisation centres have been the subject of subsequent alteration and/or reuse. As a short-lived and rare monument type, all mobilisation centres with surviving remains sufficient to give a clear impression of their original form and function are considered to be nationally important.

Henley Fort, the most westerly of the mobilisation centres within the London Defence Positions, survives well and, despite some modern renovation, retains evidence relating to its construction and use. It includes the unusual addition of a guardsroom, designed to provide further protection at the entrance of the compound.


The monument includes the main compound of Henley Fort London mobilisation centre, situated on the Hog's Back, a ridge of the North Downs, on the south western outskirts of Guildford. This location enjoyed panoramic views across the surrounding landscape. The main compound is broadly oval in plan and is defined by an earthen rampart, with a shallow, unrevetted ditch on its southern front and an outer bank beyond. Contained within the bottom of the ditch were spiked railings, known as a Dacoit fence. These extended to the rear, or gorge, of the installation, completely enclosing the compound. The gorge is approached by a roadway from the east, linked to the main access route south of the compound, and was made defensible by loopholes in its north east facing wall. Access to the interior is through loopholed steel doors, opening onto the north western side of the central parade. The entrance is approached by a passage through the rampart, which is flanked by the inturned, concrete walls of the gorge. The entrance is further protected by loopholed steel shutters which open onto the passage from a guardroom, built into the rampart behind the concrete wall, on its north western side. Set into the rear of the forward rampart, on the southern side of the parade, is a three roomed magazine block, flanked by casemates. To minimise the risk of explosion, the magazine chambers were lit by lamps set in recesses behind panes of glass, and accessed from the lamp passage which surrounds the magazine. The corridor in front of the chambers contains a shifting lobby, where magazine personnel changed into protective and non-spark producing clothes. Its outer wall is pierced by two issuing hatches, through which ammunition was passed for collection. Small chambers, located close to the entrances at each end of the magazine passage, were designed to store fuses and lamps. Water was supplied to the interior from an underground, rainwater collection tank, situated outside the entrance. The supply was supplemented by water cisterns, set into the wall on either side of the magazine, and fed through downpipes, from the gutters above. Concrete steps at each end of the parade led up to a forward parapet on top of the rampart, allowing the mobilisation centre some degree of self-defence in the event of an enemy bombardment. Steps were added to the outer face of the rampart during the early 20th century, giving access to the western portion of the ditch, and several buildings added to the compound, now mostly removed or replaced. Following the abandonment of the London Defence Positions, the site was sold in 1907, and later requisitioned during World War II when it was manned by the Home Guard. The site is currently used by the local authority as a field study centre for schools, and has been partly renovated in recent years. Associated with the main compound are the original semi-detached pair of caretakers cottages and the mobilisation tool store, situated on the approach road, to the north east of the entrance. These are now occupied as private residences and are therefore not included in the scheduling. The modern classroom building, constructed close to the outer edge of the ditch in the west, is also not included. A number of other features within the area of the monument are excluded from the scheduling. These are: the modern shower block on the northern side of the parade; the lavatory building within the western section of the ditch; all components of the modern plumbing and electrical systems; the modern surfaces of tracks and paths; all modern fences and all modern fixtures and fittings, including modern materials and office equipment stored within the compound, and components of the outdoor assault course and open air theatre, constructed within the ditch. The ground beneath these items is included in the scheduling, together with structures related to the military use of the site, to which some of these features are attached.

MAP EXTRACT The site of the monument is shown on the attached map extract. It includes a 2 metre boundary around the archaeological features, considered to be essential for the monument's support and preservation.


The contents of this record have been generated from a legacy data system.

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Books and journals
Smith, V, 'Post-Medieval Archaeology' in Chatham and London: The Changing Face of English Land Fortification 1870-1918, , Vol. 19, (1985), 105-149
Beanse, A and Gill, R, The London Mobilisation Centres - unpublished gazetteer, 1999,


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

End of official listing

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