MM044

Twm-Barlwm Mound and Bailey Castle  

15/09/1933  

Designated  

Caerphilly  

Risca  

324222  

192610  

Defence  

Motte  

Medieval  

The following provides a general description of the Scheduled Ancient Monument. The monument comprises the remains of an Iron Age hillfort with a medieval, probably Norman, Motte at the E end. The monument occupies a spectacular position on a conical shaped hill at the W end of Mynydd Henllys. The hill slopes steeply on all sides, and there are panoramic views in all directions. The ramparts of the original hillfort extend around the oval hilltop enclosing an area of roughly 9 acres. On the S side the inner bank is 0.4m high, dropping 3m to the base of the ditch. The ditch is up to 2m wide with a 1.5m counterscarp bank on the external edge. Halfway along the S side is a 40m wide gap in the defences, with a second 40m wide gap at the SW corner and several short, interrupted, sections of bank and ditch to either side of it. Excavations in 2021 and 2022 revealed that the gaps in the S and W ramparts are original features of the hillfort, not the result of later damage or destruction. The foundations of a stone field wall follow the line of the enclosure where the W ramparts are missing, this is depicted on the 1st edition OS map and relates to the post-medieval use of the hill. Along the N side the bank and ditch are continuous and notably larger with the bank up to 1.5m high on the inside, dropping 4m to the base of the ditch. The ditch is up to 3m wide and has a 1.7m high counterscarp bank on the external edge. Excavations in 2021 revealed that the original ditch was rock cut, 7m wide and 4m deep. Dating of charcoal from the initial silting deposit demonstrated it to have been constructed in the later Iron Age. Investigations of the inner rampart on both the N and S sides of the hillfort revealed that it comprises randomly deposited dumps of stone with no structure and no soil bonding. The stones look to have been excavated from the rock cut ditch but no attempt had been made to form a stable bank. The lack of bank structure together with the large gaps in the S defences suggest that the hillfort was never completed. The motte is located at the E end of the hilltop and was constructed over the line of the Iron Age ramparts. It is steep-sided, 7m high with a flat summit 17m in diameter. On the W side of the motte is a rock-cut ditch, 2.5m deep and 4m wide with near vertical rock faces. Excavation in 2022 revealed that the original ditch was V-shaped and cut into the bedrock to a depth of approximately 6m. On the E and S sides is a shallow ditch, around 1m deep, while on the N side there is no ditch. The motte is likely to date from the early post-conquest period although its original function is unknown. The interior of the hillfort is gently sloping with a Trig Point positioned close to the middle. At the E end, adjacent to the ditch surrounding the motte is a probable Bronze Age burial cairn consisting of a roughly circular mound of stones around 7m in diameter. Partial excavation of the mound in 2022 revealed some evidence for a kerb defining the edge of the cairn but no dating evidence. On the S side of the interior is an extensive area of ridge and furrow of unknown date by probably related to the post-medieval use of the hill. The monument is of national importance for its potential to enhance our knowledge of later prehistoric and medieval defensive organisation. The well-preserved monument forms an important element within the wider later prehistoric and medieval context and the structure itself may be expected to contain archaeological information relating to chronology, building techniques and functional detail. The scheduled area comprises the remains described and areas around them within which related evidence may be expected to survive.