Fosterdown or Pilgrim Fort: a London mobilisation centre


Heritage Category: Scheduled Monument

List Entry Number: 1019288

Date first listed: 27-Jul-1973

Date of most recent amendment: 07-Jun-2000


Ordnance survey map of Fosterdown or Pilgrim Fort: a London mobilisation centre
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The building or site itself may lie within the boundary of more than one authority.

County: Surrey

District: Tandridge (District Authority)

Parish: Caterham Valley

National Grid Reference: TQ 34422 53336


Legacy Record - This information may be included in the List Entry Details.

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.

Despite some alteration and renovation, Fosterdown Fort survives comparatively well, and will retain evidence relating to the construction and use of mobilisation centres.


Legacy Record - This information may be included in the List Entry Details.


The monument includes the main compound of Fosterdown Fort, also known as Pilgrim Fort, situated on a southern spur of the North Downs, around 1km south of Caterham. The main, south facing compound, is roughly circular in plan and is defined by a large, earthen rampart. The shallow, surrounding ditch, which is in turn encircled by a low bank, contained spiked metal railings which completely enclosed the compound. Access to the interior is from the gorge to the north or rear of the compound through a gap in the rampart, which is flanked by low concrete walls which meet its rear-curving ends. The entrance is approached by a track from the north, and opens onto an almost square, north west-south east aligned central parade. Its concrete walls, on the north eastern and western sides, extend to join the low gorge walls. The parade is defined on its south western side by a three roomed magazine, set into the rear of the forward rampart, just below the internal ground level. 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 was divided into two sections by the addition of a partition wall. The short passage in front of the cartridge store contained a shifting lobby, just inside the entrance, where magazine personnel changed into protective and non-spark producing clothes. A separate entrance for the two shell stores, in the south eastern portion of the magazine corridor, also provided access to the lamp passage and two small chambers designed to store lamps and fuses. On either side of the partition wall, the outer wall of the corridor is pierced by two issuing hatches, through which ammunition was passed outside for collection. The magazine retains many of its original features, including two windows facing into the parade, and wooden shutters in the ceiling of the shell stores, designed to control the circulation of air through the ventilation ports. A four roomed casemate block, set into the rampart just below ground level, defines the south eastern side of the parade. At each end of the casemates, steps lead up from the parade onto the top of the rampart, which could function as a firing parapet, allowing the mobilisation centre some degree of self-defence in the event of enemy bombardment. After the London Defence Positions were abandoned, in around 1905, the centre was finally sold in 1920. It was subsequently used, for much of the 20th century, as a field study centre for school groups. To meet their needs, the casemates were converted into washrooms and drying rooms, and two brick chimney stacks were constructed on the flat roof, above the ventilation shafts. Associated with the main compound are the original, semi-detached pair of caretakers' cottages and the mobilisation tool store, situated on the eastern side of the approach road from the north. The cottages, situated around 80m north of the compound, have been converted into a private residence, and the mobilisation tool store, which is Grade II Listed, located just outside the entrance, is undergoing conversion for an alternative use. These buildings are therefore not included in the scheduling. A number of features within the area of the monument are excluded from the scheduling. These are: all modern fences; all modern fixtures and fittings, including all components of the modern electrical and plumbing systems, as well as modern materials and equipment stored within the mobilisation centre; and the wooden sheds, constructed on the north eastern edge of the rampart and ditch. The ground beneath these items is included in the scheduling, together with structures and surfaces 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.


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

Legacy System number: 32276

Legacy System: RSM


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,

End of official listing