1. A large promontory fort of approximately 1.7 hectares in area. The defences are built across the narrowest part of the promontory which is here about 60m wide. These defences consist of three lines. The outermost is a rock-cut ditch about 4m wide and 2m deep, rather square cut. On the inner side there are two banks the first forming a central defence being the larger at about 1m high and the second innermost bank somewhat less. Although the defended area contains a great deal of habitable level space there are no visible signs of any dwellings or structures, although a possible roundhouse was noted in 1963, but has not been confirmed.The cliff edge wall, which is a more of less continuous feature on this property is built on the landward side of the defences but quite close to the rock-cut ditch. It is a very well consolidated structure here. 40m above O.D.

John Latham RCAHMW 30 July 2013

2. In November 2022, a partial collapse was reported effecting the south-western tip of the promontory fort. Rotational slumping of some 40m of cliff had occurred, in a geologically weak area on the southern cliff line which had already cut a section out of the headland. The erosion was recorded during Royal Commission aerial reconnaissance on 15th December 2022 (frames: AP_2022_3524-36), and through using a 6m photo pole and GoPro during a field visit on 27th July 2023. The slump has dropped between 1-1.5m away from the former land surface, but is full of dangerous and unstable voids.

T. Driver, RCAHMW, 31 July 2023.

3. On the 22 November 2023 the Royal Commission undertook UAV photogrammetric survey and a GNSS topographic/earthwork survey of the monument.

A model resulting from the UAV survey is viewable here: https://skfb.ly/oOSBG

Monument Description

The monument comprises the remains of a coastal promontory fort, most likely of Iron Age date (c.800BC – AD43). It is situated on a narrow promontory above the sea, with cliffs on three sides, and a triple line of defence (spanning 40 metres), constructed across the narrowest part of the promontory on the landward side, today a width of some 35 metres.

The defences predominantly survive in earthwork form and comprise an outer rock-cut ditch with an internal scarp slope. The ditch measures 5 metres in width and is 1.5 metres deep. It runs for 40 metres from the coastal edge /coastal slope at its northern end to a clear terminal at its southern end, which likely marks the original entrance approach into the fort. The rock face is clearly exposed on the outer (east) face of the ditch. It is possible that this might be the result of later quarrying associated with the stone wall adjacent to the site. This wall was constructed between the 1st and 2nd editions of the 25-inch Ordnance Survey Maps which were published in 1889 and 1907. To the south of the ditch a further rock outcrop also exhibits signs of quarrying.

The scarp slope sits immediately inside the outer ditch, standing 2 metres high from base of the ditch. At its northern end the scarp deviates from the ditch turning west for some 12 metres and runs up to the cliff edge and links with the second (middle) line of fort defences. It is unclear the exact purpose of this arrangement, but as it runs across and cuts off an area of coastal slope, its objective may have been to strengthen an otherwise vulnerable area. At its southern end, defining the entrance, the scarp also turns and links with the second line of defences. In the intervening space a slight mound is evident, 0.5m high, which may indicate the presence of an entrance/gateway structure.

The second (middle) line of defence comprises a bank and ditch, running from the coast edge on the north. The ditch is largely infilled and measures 3.6 metres wide and 0.6 metres deep. It is visible for some 14.6 metres. Set 1.5 metres back from the ditch is the bank, 5.2 metres wide and 0.8 metres high. An entrance, presumably original?, cuts through the bank near its southern end, comprising a simple gap 2.1 metres wide. To the south of this entrance a short section of the bank then merges with the coastal slope and exposed rock. Cut into the bank on either side of the entrance are two circular pits, the one to the north the most distinct, some 3 metres in diameter and 0.3 metres deep. This is unlikely to be an original feature and most likely a result of later digging.

The third line of defence is the least visible and comprises a bank and ditch set 4 metres back from the second line. These again run from the coast edge to the north, with the 16.8 metre long section to the north of the presumed entrance the clearest. Beyond this a very slight earthwork may suggest the original continuation to the south of the entrance. The ditch is 2.8 metres wide and 0.3 metres deep. The bank rises straight from the ditch and is 2.5 metres wide and 0.2 metres high. A possible small section of walling was exposed in the inner face of the bank at SM 84047 33830. At the northern end there is a slight suggestion of a second internal ditch, but this is only visible for around 7 metres and is only 0.2 metres deep.

The interior of the promontory fort today encompasses an area of 12,700 square metres (1.27 hectares), and there is clear evidence of erosion on all sides of the interior. A visit by RCAHMW on 7 May 1920 during fieldwork for the Pembrokeshire Inventory, noted that the fort had been disturbed by a landslide (1925: pg 177 No. 523). The recent 2023 landslide is clearly visible at the south-western tip, where a 37 metre long edge is now clear, beyond which an area of 405 square metres has slumped.

The central section of the interior comprises largely level ground - 37 metres above sea level. To the north and south of this is coastal slope running down to the rocky cliffs defining clear coast edge. There is no evidence of structures or features in the interior, which is under tussocky grass.

Research History

One of the earliest plans and description of the monument is by Barnwell (1875, 80 and Figure 1) where he notes it’s alternative name as Penrhyncoch. At this date he notes there was no surface evidence of habitation in the interior. Shortly after a more accurate survey of the fort is depicted on the First Edition 25-inch Ordnance Survey map published in 1889.

The fort is marked and noted on the 1908 Archaeological Survey of Pembrokeshire, which used the Ordnance Survey 2nd edition 25-inch map of 1908 as its base (Sheet VIII. S.E.). It is described as strongly fortified with traces of 4 ditches and 3 ramparts ‘much worn’. Noted here, but not described in other sources is ‘a large cavern high above the sea on the promontory where the cliff has now fallen in’ (Laws and Owen 1908: 15).

The RCAHMW 1925 Pembrokeshire inventory includes the promontory fort (pg 177: No. 523), describing the defences across the neck as ‘two strong earth and stone banks, and two intermediate platforms or shallow ditches’. The entrance is noted as between the southern end of the ramparts and the cliffs.

Castell Coch is included in Crosley’s list of hill-forts and earthworks in Pembroekshire published in 1963 (177, No. 21). It is described as a having a ‘bivallate defence across promontory neck. Slight inside ditch. Entrance probably at north end of bank. Circular structure in centre of enclosure’. This description alongside the mention of a circular structure does not correspond to any of the other descriptions and tit must be considered as erroneous.

A field visit by the Ordnance Survey in 1966 (Record Card: SM83SW12), notes the strongest feature being the outer rock cut ditch, that the entrance was not clear, but was probably in the south and there was no trace of any internal structures.

The promontory fort was included in the survey of defended enclosures in Pembrokeshire undertaken by Dyfed Archaeological Trust ion 2006-07 (Heneb: PRN 2848).

Castell Coch is a Scheduled Monument (PE029) and is located on National Trust land.

Louise Barker, RCAHMW, 12 June 2024

Sources

Barnwell, E. L. , 1875, ‘Pembrokeshire Cliff Castles’, Archaeologia Cambrensis, Vol VI 4th Series, 74-86.

Cadw Scheduled Monumnet PE029: https://cadwpublic-api.azurewebsites.net/reports/sam/FullReport?lang=&id=3336

Crossley, D.W., 1963, ‘List of Hill-Forts and Other Earthworks in Pembrokeshire’ Bulletin of the Board of Celtic Studies, Vol. 20, 171-206.

Downman, E. A. List of Ancient Earthworks in Pembrokeshire surveyed and drawn by Edward Andrews Downman c1910-1913 (Pembrokeshire Archives: HDX/1092/43).

Driver, T. 2007, Pembrokeshire, Historic Landscapes from the Air, RCAHMW, page 102, Figure 152.

Heneb: Dyfed HER PRN 2848 https://archwilio.org.uk/her/chi3/report/page.php?watprn=DAT2848&dbname=dat&tbname=core&sessid=CHI3q8g76g2&queryid=Q650644001718119211

Laws, E. & Owen, H., 1908, An Archaeological Survey of Pembrokeshire (National Library Wales). https://www.peoplescollection.wales/items/13011#?xywh=524%2C-121%2C1393%2C1416&cv=31

Murphy, K., Ramsey, R., Poucher, P. and Page, M, 2007, A Survey of Defended Enclosures in Pembrokeshire, 2006-07: Gazetteer of Ordnance Survey Grid Squares SM73, SM83 & SM93 (Unpublished: Dyfed Archaeological Trust)

National Trust Heritage Record. ID 82801 / MNA134090 https://heritagerecords.nationaltrust.org.uk/HBSMR/MonRecord.aspx?uid=MNA134090

Ordnance Survey 1st Edition 25-inch map (published 1889)

Ordnance Survey National Record Card: SM83SW12 (available at RCAHMW).

RCAHMW, 1925, An Inventory of the Ancient Monuments in Wales and Monmouthshire. VII- County of Pembroke (pg 177: No. 523).

RCAHMW Photgrammetric Survey 22/11/2023: https://skfb.ly/oOSBG

Site Record

Castell Coch Promontory Fort, Trefin