Reasons for Designation
Promontory forts are a type of hillfort in which conspicuous naturally defended sites are adapted as enclosures by the construction of one or more earth or stone ramparts placed across the neck of a spur in order to divide it from the surrounding land. Coastal situations, using headlands defined by steep natural cliffs, are common while inland similar topographic settings defined by natural cliffs are also used. The ramparts and accompanying ditches formed the main artificial defence, but timber palisades may have been erected along the cliff edges. Access to the interior was generally provided by an entrance through the ramparts. The interior of the fort was used intensively for settlement and related activities, and evidence for timber- and stone- walled round houses can be expected, together with the remains of buildings used for storage and enclosures for animals. Promontory forts are generally Iron Age in date, most having been constructed and used between the sixth century BC and the mid-first century AD. They are broadly contemporary with other types of hillfort. They are regarded as settlements of high status, probably occupied on a permanent basis, and recent interpretations suggest that their construction and choice of location had as much to do with display as defence. Promontory forts are rare nationally with less than 100 recorded examples. They are also important for understanding of the nature of social organisation in the later prehistoric period. The promontory fort known as Treryn Dinas survives particularly well and will contain archaeological and environmental evidence relating to its construction, development, use, defensive and territorial significance, social organisation, agricultural, economic, industrial and trading activities and domestic arrangements as well as its overall landscape context.
The monument includes a promontory fort, situated on a small rocky headland known as Treryn which has a flat summit and slopes steeply to the sea on three sides. The promontory fort survives as three main lines of artificial defence to the landward, or northern side, the other sides being defended by steep natural cliffs effectively enclosing an area of up to 6 hectares. The innermost rampart extends across the narrowest neck of the headland. It measures up to 2m high, and is composed of coursed stones with a central inturned entrance with stone jambs. There is a distinct V-shaped ditch. The small enclosed area behind the rampart contains two slightly oval hut platforms. The central defences consist of two curving ramparts, both or which are relatively low rubble banks with no facing stones and a outer ditch and counterscarp bank. The outermost rampart and ditch are both massive with a simple causewayed entrance. The earth and stone rampart is up to 6.1m high. To the west of the entrance, stone for the rampart was also obtained from an inner quarry ditch measuring up to 9m wide. The promontory is also famous for its Logan or 'rocking' stone.
The fort was first recorded by Borlase in the mid-18th century and is named Trereen Castle on the 1813 Ordnance Survey map. Blight also recorded it and noted that a Roman coin was said to have been found nearby. Antiquarian reports of a cist and possible stone circle within the promontory fort are now regarded as natural features or misinterpretations of construction techniques used in the ramparts. Flints and a rubbing stone have been variously reported as surface finds since the 19th century.
PastScape Monument No:-421380, 421400, 421403 and 421413