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Cof Cymru: National Historic Assets of Wales · Wales

Tresilian Bay Anti-invasion Defences

St. Donats, Vale of Glamorgan, Wales

The record

Designation
Scheduled monument
Site type
Pillbox
Period
Modern
Date of designation
28 October 2019
Welsh name
Amddiffynfeydd Gwrthoresgyniad Bae Tresilian (GM617)
Community
St. Donats
Unitary authority
Vale of Glamorgan
Country
Wales
Coordinates (centre of the scheduled area)
51.39916, -3.51699
SAM number
GM617
Cadw record number
4379

Slide toward Today to fade the historical sheet and see the modern map underneath.

David Rumsey Map Collection, Stanford Libraries

Shown on 5 historical map sheets, the earliest the 1858 "20. Bridgewater." (David Rumsey Map Collection, Stanford Libraries).

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This record in Cadw's own full report ↗

Cadw's description

The monument consists of anti-invasion defences (6 reinforced pillboxes), dating to the early period of the Second World War (AD 1940-41) that formed part of Western Command's Glamorgan coastal crust defences. They are aligned east – west, extend for 850m overlooking the gently shelving beach at Tresilian Bay to the south and are lettered A to F on the map attached to this entry. Four are of regular hexagonal design with low protected entrances located on the edge of tall limestone cliffs (A, B, C and F), whilst the other two (D and E) are of unique designs located above the high water mark at the north western and north eastern corners of Tresilian Bay. Pillboxes A, B and C are built of reinforced concrete with external red brick shuttering and D and E were carefully camouflaged with limestone blocks to match the adjacent cliff faces. Pillbox F is built of reinforced concrete with external limestone facing.

The monument is of national importance for its potential to enhance our knowledge of Second World War anti-invasion practices. It is well preserved and is an important relic of actions taken against the perceived threat of a German invasion from Ireland. It retains significant archaeological potential, with a strong probability of the presence of associated archaeological features and deposits. The importance of the monument is enhanced further by its internal group value, together with the group value it shares with adjacent anti-invasion defences to the East (Limpert Bay Anti-invasion Defences (GM601)).

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

• Areas A, B, C and F are centred on SS 94168 67887, SS 94439 67846, SS 94675 67723 and SS 94961 67660 respectively, and are circular measuring 15m in diameter.
• Areas D and E are centred on SS 94750 67770 and SS 94808 67729 and are square measuring 12m N-S by 12m transversely.

Nearby in the register

Other entries of the same register within about three miles of this one, by straight line.

Designated Historic Asset GIS Data, The Welsh Historic Environment Service (Cadw), 2026-09-07, licensed under the Open Government Licence http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ Cadw, the Welsh Historic Environment Service · Open Government Licence v3.0
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