Blog – Pembrokeshire’s Prehistoric Promontory Forts – Shifting coastlines and perceptions (RCAHMW)

It is hard to deny that Pembrokeshire’s coastline is amongst the finest in the British Isles in terms of its beauty and diversity. Most people who walk along the famed Pembrokeshire coastal path will come away stunned by what they see, and it easy to see why. However, when asked if they had noticed any of the 50+ prehistoric promontory fort sites on their journey many will remark at how they encountered some ‘strange humps and bumps’ but nothing out of the ordinary. This is a far cry from the Prehistoric Period where many of these sites would have been focal points in a busy prehistoric Pembrokeshire landscape, and extremely visible both from the land and the sea. Modern perceptions of these sites and their associated land and seascapes have moved far beyond those of their builders, with climate change and coastal erosion playing a key part in this perceptual shift.

Promontory forts are one of the most abundant classes of archaeological monument in the county but so little is known about them. Their density along the coastline suggests that they were important components of the prehistoric landscape, but their functions are not clear. Excavations have been extremely limited, hindering the reliability of interpretations. Porth y Rhaw to the south east of St Davids is one of the few sites to have benefitted from intrusive investigations where extensive evidence of several phases of settlement from the early-mid Iron age period to the 4th century AD were uncovered. Based on this work many promontory forts in the county have been interpreted as places of settlement for coastal communities to live and work while maintaining easy access to the sea. Whilst this interpretation may be true for most, vast differences in the size and layout of defences, interior space, likely functions, and access to the sea means that the catchall term ‘promontory fort’ is actually used to describe a hugely diverse class of monument. These sites are not only present in Pembrokeshire but along many coastlines that face out to the Irish Sea, English Channel and the Atlantic, extending their significance beyond the borders of Wales.

An aerial photograph of Porth y Rhaw promontory fort taken from a manned aircraft showing its series of enclosing defences and heavily eroded interior. Evidence of roundhouses was discovered through excavation in the eastern portion of the surviving interior (top of picture). Evidence of scoops relating to possible settlement was discovered by analytical earthwork survey on the western slopes of the fort (bottom of picture).

An aerial photograph of Porth y Rhaw promontory fort taken from a manned aircraft showing its series of enclosing defences and heavily eroded interior. Evidence of roundhouses was discovered through excavation in the eastern portion of the surviving interior (top of picture). Evidence of scoops relating to possible settlement was discovered by analytical earthwork survey on the western slopes of the fort (bottom of picture).

Whilst plentiful, promontory forts face a stark lack of understanding, made worse by the fact that they have been suffering from coastal erosion for centuries, traceable through analysing historic maps and aerial photographs. Not only has erosion led to the loss of potential archaeology key to understanding the site’s history but has also influenced the way they are perceived and managed by people today.

Work by CHERISH has aimed to improve the understanding of these sites and monitor them for coastal erosion through the use of several traditional and modern surveying techniques. For a selection of sites this has involved carrying out analytical earthwork surveys using GNSS equipment to record all archaeological features visible on the surface, which in the case of coastal promontory forts largely comprises the defensive earthworks. Not only have these surveys helped guide how sites are managed but they have provided an opportunity to think about them in a more critical way than before. At Porth y Rhaw a more meaningful interpretation of the large defences augments the findings of the numerous excavations. Several phases of defence construction along with numerous possible hut scoops were identified, adding another dimension to this site. At Caerfai Camp, a site which exhibits a unique series of four large banks and ditches, at least two phases of defence construction were identified. Earthworks relating to the route into the fort also provoked thoughts surrounding the function of the defences. Compared to the huge bank and ditch defences the entranceway appears to have lacked any form of defensive structure which begs the question whether this was a fort built for defence or to merely impress visitors. Geophysical survey of Caerfai’s interior, although partially obscured by geological interference, also interestingly revealed a stark lack of buried archaeological remains.

An aerial photograph taken by UAV of Caerfai Camp promontory fort showing its substantial defences formed of a series of four banks and ditches. Much of the large interior still survives but coastal erosion will eventually cut-off much of the promontory fort from the mainland, forming a new island.

An aerial photograph taken by UAV of Caerfai Camp promontory fort showing its substantial defences formed of a series of four banks and ditches. Much of the large interior still survives but coastal erosion will eventually cut-off much of the promontory fort from the mainland, forming a new island.

UAVs have also been used to good effect where they have not only helped to provide centimetre accurate baseline data for monitoring coastal erosion but objective 3D data that can be used for further archaeological interpretation and dissemination. Numerous sites have been recorded in both Wales and Ireland using similar equipment and techniques, resulting in some lovely data and products. In Pembrokeshire, both Caerfai Camp and Porth y Rhaw have been recorded using this method, with more surveys planned for sites situated within the Castlemartin firing range such as Linney Head and Flimston Bay promontory forts. 3D models of sites in Wales and Ireland have been created using UAV derived data and can be viewed here.   

Conducting this sort of work on Pembrokeshire’s promontory forts is important for not only furthering the archaeological understanding of the monuments but raising awareness of them to the public, both in terms of their cultural value and the threats they face from climate change and coastal erosion. Archaeological survey and research work to provide the stories behind the monuments that now seemingly stand isolated along our coastlines, whilst erosion monitoring helps to make sense of how they are physically changing and the physical impacts upon the archaeology. Raising awareness of the archaeological stories and climate change issues is important as society moves forward and the preservation of archaeological sites slip down the agenda. This is especially pertinent to Pembrokeshire’s promontory forts which are a testament to the rich history of the region. Losing them to the unforgiving claws of climate change before we understand them as best we can would be a tragedy locally, national and internationally. CHERISH will continue with this objective over the coming years.

An archaeological earthwork survey in progress at Porth y Rhaw. By using highly accurate GNSS survey equipment, CHERISH has been able to record threatened monuments to extremely high levels of detail, recording them both for archaeological discovery and in perpetuity for ongoing erosion monitoring.

An archaeological earthwork survey in progress at Porth y Rhaw. By using highly accurate GNSS survey equipment, CHERISH has been able to record threatened monuments to extremely high levels of detail, recording them both for archaeological discovery and in perpetuity for ongoing erosion monitoring.

Dan Hunt – CHERISH Project Investigator