Ancient Monuments

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Tresilian Bay Anti-invasion Defences

A Scheduled Monument in St. Donats (Sain Dunwyd), Vale of Glamorgan (Bro Morgannwg)

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Latitude: 51.3992 / 51°23'57"N

Longitude: -3.5169 / 3°31'0"W

OS Eastings: 294574

OS Northings: 167776

OS Grid: SS945677

Mapcode National: GBR HH.R03T

Mapcode Global: VH5J5.0346

Entry Name: Tresilian Bay Anti-invasion Defences

Scheduled Date: 17 May 2019

Source: Cadw

Source ID: 4379

Cadw Legacy ID: GM617

County: Vale of Glamorgan (Bro Morgannwg)

Community: St. Donats (Sain Dunwyd)

Built-Up Area: St Donat's

Traditional County: Glamorgan


The monument consists of anti-invasion defences, 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 E-W and extend for 850m overlooking the gently shelving beach at Tresilian Bay to the S. The monument consists of six reinforced pillboxes. Four are of regular hexagonal design with low protected entrances located on the edge of tall limestone cliffs (Items A, B, C and F), whilst the other two (Items D and E) are of unique designs located above the high water mark at the NW and NE corners of Tresilian Bay. Items A, B and C are built of reinforced concrete with external red brick shuttering. Items D and E were carefully camouflaged with limestone blocks to match the adjacent cliff faces. Item 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 E (Limpert Bay Anti-invasion Defences (GM601)).

The areas to be scheduled comprise the remains described and areas around them within which related evidence may be expected to survive. Area A is centred on Item A at SS 94168 67887. It is circular and measures 15m in diameter. Area B is centred on Item B at SS 94439 67846. It is circular and measures 15m in diameter. Area C is centred on Item C at SS 94675 67723. It is circular and measures 15m in diameter. Area D is centred on Item D at SS 94750 67770. It is square and measures 12m N-S by 12m transversely. Area E is centred on Item E at SS 94808 67729. It is square and measures 12m N-S by 12m transversely. Area F is centred on Item F at SS 94961 67660. It is circular and measures 15m in diameter.

This monument has been afforded Interim Protection under the Ancient Monuments and Archaeological Areas Act 1979. It is an offence to damage this monument and you may be prosecuted.

To find out more about Interim Protection, please visit the statutory notices page on the Cadw website. For further information about this monument, or to report any damage please contact Cadw.

Source: Cadw

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