Alderstead Fort: a London mobilisation centre at Merstham


Heritage Category:
Scheduled Monument
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Ordnance survey map of Alderstead Fort: a London mobilisation centre at Merstham
© Crown Copyright and database right 2019. All rights reserved. Ordnance Survey Licence number 100024900.
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The building or site itself may lie within the boundary of more than one authority.

Reigate and Banstead (District Authority)
National Grid Reference:
TQ 29523 54536, TQ 29565 54592

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.

Unusually for this type of monument, Alderstead Fort has remained largely free of alteration or renovation and, despite some natural decay and woodland regeneration, survives comparatively well. Architectural survey has shown that the monument retains evidence relating to the construction and use of mobilisation centres.


The monument falls into two separate areas and includes the main compound and tool store of East Merstham mobilisation centre, known as Alderstead Fort, situated on a chalk ridge of the Surrey Downs. The main compound forms the south western part of the monument and houses a three-roomed magazine fronted by five casemates. It survives as a roughly north west-south east aligned, north east facing, flat-roofed structure constructed mainly of reinforced concrete and brick, with a large, crescent- shaped earthen blast-bank partly covering and flanking the magazine to the rear. Beyond the bank is an up to 10m wide ditch. The building retains many original fittings, including iron-and-wood door and window shields and magazine vents. The associated red-brick tool store lies around 75m to the north east and is a north east-south west aligned, single storey, rectangular building measuring 14m by 10m, with white washed sandstone dressings under a pitched, blue slate roof. The south eastern face has full-length, central double doors flanked by tall windows with iron grilles. The original caretaker's lodge, situated around 40m to the north east, is in use as a dwelling and is therefore not included in the scheduling. The modern lean-to structures at the north western end of the main compound are excluded from the scheduling, although the ground beneath them is included.

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, 'London Archaeologist' in The London Mobilisation Centres, , Vol. 2, 10, (1975), 244-248
Gill, RJ, East Merstham Mobilisation Centre, 1995, unpublished survey


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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