Ancient Monuments

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Flat Holm Coastal and Anti-aircraft Defences

A Scheduled Monument in Sully and Lavernock (Sili a Larnog), Vale of Glamorgan (Bro Morgannwg)

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Latitude: 51.3766 / 51°22'35"N

Longitude: -3.1218 / 3°7'18"W

OS Eastings: 322014

OS Northings: 164768

OS Grid: ST220647

Mapcode National: GBR J0.SHFX

Mapcode Global: VH6FT.TNZK

Entry Name: Flat Holm Coastal and Anti-aircraft Defences

Scheduled Date: 15 January 2008

Source: Cadw

Source ID: 1237

Cadw Legacy ID: GM595

Schedule Class: Defence

Category: Battery

Period: Post Medieval/Modern

County: Vale of Glamorgan (Bro Morgannwg)

Community: Sully and Lavernock (Sili a Larnog)

Traditional County: Somerset


The monument consists of two pairs of dual-purpose anti-aircraft and anti-shipping gun emplacements, which date to the mid- and later periods of World War II (AD 1941-5). The South Battery comprises a pair of gun emplacements (Item B), a command post (Item A), magazine (Item C) and a pair of coastal artillery searchlight emplacements (Items D and E). The North Battery comprises a pair of gun emplacements (Item G), a command post (Item F), magazine (Item H) and a pair of coastal artillery searchlight emplacements (Items I and J). Both batteries shared a common radar receiver platform (Item K). The structures formed part of the Fixed Defences, Severn scheme and protected the Atlantic shipping convoy de-grouping zone between Cardiff, Barry and Flat Holm, as well as contributing to the overall coastal defence of port installations in the upper Bristol Channel and the anti-aircraft defence of Cardiff docks. The structures were constructed from combinations of brick, reinforced concrete and hollow concrete brick. Many of the structures are concealed and protected by being part buried into the ground surface and / or surrounded by an external bund of earth and stone.

The monument is of national importance for its potential to enhance our knowledge of World War II defensive practices. The monument is very well preserved due to its isolated location. It retains significant archaeological potential, with a strong probability of the presence of associated archaeological features and deposits. The importance of the monument is further enhanced by the collective group value of the structures.

The areas scheduled comprise the remains described and rectangular areas around within which related evidence may be expected to survive.

Source: Cadw

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