Late Bronze Age / Early Iron Age (c. 800–400 BCE)

No documentary evidence for Twmbarlwm is currently known, and it is stated that it has not always been classified either as a hillfort or as a motte. Many scholars believe Twmbarlwm Hillfort originated in the late Bronze Age or early Iron Age, during a period marked by increasing social organisation, population pressure, and a shift in power structures, often materialised in the construction of hillforts. These fortified enclosures served a range of possible functions—defensive refuges, social centres, storage hubs, or status symbols for emerging tribal elites. A bronze age cairn has been identified within this monument, to the west of the motte ditch and has been interpreted as a funerary round cairn, probably dating from the late Neolithic or early Bronze Age. The feature comprises a circular mass of stones and was formed from quarried stone slabs. It has a hollow centre suggesting the mound was robbed to recover any artefacts at some point in the past. In the wider area is a linear grouping of four prehistoric cairns situated 752m to the west of the site, and a single Bronze Age cairn located across the valley 3km to the south-west.

Constructed using earth and stone, the enclosure occupies a commanding ridge position on Mynydd Twyn-glas at 419 metres above sea level offering extensive views over the Ebbw and Usk valleys. Its strategic location suggests a defensive function, possibly serving as a stronghold, refuge, or territorial marker, perfect for surveillance, control of movement, and communication. The motte is surrounded by a rock cut ditch to the south, west and north, and the ditch cuts the Iron Age ramparts with a berm added. The rampart bank and ditch become less distinct in a section to the west and originally considered to be the result of an unfinished defensive circuit. However, whilst the defences here are considered weak, archaeological works in 2021 revealed that this is likely the entrance to the site due a to lack of evidence of backfilling.

Iron Age (c. 400 BCE – 43 CE)

By the middle to late Iron Age, Twmbarlwm Hillfort was likely well established and may have played a key role in the local settlement hierarchy. Archaeological parallels suggest it may have functioned as a settlement or community centre with timber roundhouses, granaries, and livestock enclosures, all surrounded by defensive ramparts and ditches. It likely continued to serve as a focal point for the local population, possibly the Silures, a prominent Celtic tribe of south-east Wales known for their resistance to Roman invasion. The site’s prominence would have reinforced its role in social, economic, and possibly ritual activities within the wider landscape. The construction and maintenance of such a site would have required communal effort, suggesting strong social cohesion and leadership.

From the prehistoric period, particularly the Iron Age, charcoal and a small number of pottery sherds have been identified in the surrounding area. These are typically coarse, hand-made wares associated with domestic activity. Additionally, traces of burnt stone and charcoal have been noted on the hill, possibly indicating hearths or cooking areas. Some surface finds may include worked flint or stone flakes, although these remain poorly documented and are not securely dated.

Roman Period (43 – 410 CE)

Following the Roman conquest of Britain, the Silures mounted a fierce resistance, which led to prolonged military campaigns in south-east Wales. With the eventual subjugation of the Silures, many native hillforts were either abandoned or repurposed. Twmbarlwm’s strategic value would have diminished as the Roman military established a network of forts and roads across the region, including the nearby legionary base at Caerleon (Isca Augusta). The hillfort would have lost its military value under Roman rule, with its function likely ceasing altogether. While archaeological evidence is limited, any continued use of the site during this period was likely symbolic, ritualistic or sporadic for local populations. Although some upland sites were repurposed for pastoral use or as waypoints within Romanised territory.

Despite the strategic significance of Twmbarlwm during the Roman period, there is no direct evidence of Roman occupation on the hill itself. However, Roman pottery and other artefacts have been recovered from lower slopes and nearby sites in the Ebbw Valley, suggesting Roman activity in the broader landscape. These items may reflect trade, movement, or displaced materials rather than direct settlement at the hillfort.

Early Medieval Period (5th – 11th centuries)

After the Roman withdrawal in the early 5th century, power reverted to local rulers and tribal groupings. Although direct archaeological evidence from this period is scarce, it is plausible that Twmbarlwm may have retained its significance as a territorial boundary or ceremonial site. Its continued prominence in the landscape may have made it a natural boundary marker between emerging early medieval kingdoms or commotes. Additionally, some hillforts were reoccupied or used as assembly sites during this era, though no excavations at Twmbarlwm have confirmed such reuse. Its imposing presence would have continued to shape local identity and tradition, possibly giving rise to early folklore and oral histories.

Medieval Period (12th – 15th centuries)

The summit mound at Twmbarlwm includes a distinct mound and has been interpreted by some scholars as a possible Norman motte, suggesting that the site may have been reused as a watchtower or signalling outpost during the medieval period. The form of both the bank and ditch of this motte, at the eastern extent of the enclosure suggests that it was a medieval motte. Its lower sections, including the ditch, were cut from the bedrock, with the mound raised above this level. Phillips has categorised the site as an early watch-tower motte without a bailey, and surmises that the limit of the Norman influence would have been confined to the eastern end of the site. It may have carried a grand timber-framed tower within a small, palisaded court. At its base is a deep ditch, rock-cut in places, which appears to cut the enclosure ditch.

Knight also suggests that the motte may have been an unfinished de Clare castle built during the late 13th century, noting its similarities in location to another masonry castle at Morlais. Whilst this interpretation remains inconclusive, it would imply the Normans saw value in reusing earlier strategic sites to assert control over the region’s uplands and key travel routes. Such a watchpoint would have been especially useful in overseeing movement through the Ebbw Valley, which became more accessible with the development of medieval trackways. Wiles notes that this is an unusually remote site for a medieval castle, particularly for a lordly territorial centre, and it is possible that the castle was built as a hunting seat within Newport lordship. If the enclosure is regarded as part of the castle, this would suggest that this was a place of assembly where vassals gathered to attend on their lord. Nevertheless, there is no documentary evidence of a castle or manorial site at Twmbarlwm, suggesting any reuse was limited in scale. No associated artefacts such as medieval pottery, nails, or masonry have been confirmed. The lack of such material makes the interpretation speculative.

Post-Medieval to Modern Period (16th century – Present)

In later centuries, Twmbarlwm became embedded in local folklore, sometimes linked—albeit erroneously—with the legendary figure Twm Sion Cati. By the 18th and 19th centuries, it attracted antiquarian interest, especially during the 19th century’s Romantic movement, which idealised wild and ancient landscapes. It has since become a popular destination for communal activities and walkers and played a role in the local cultural life of south-east Wales, with Easter and Whitsun walks becoming annual traditions. Isolated finds such as coins and metalwork have reportedly been discovered in the area, often through unregulated metal detecting. These finds are typically not stratified and are difficult to associate directly with the hillfort’s primary use phases.

In the 20th century, the southern section of the rampart was breached. Whilst the circumstances remain unclear, there is speculation of an attempt to use the land to plough it for crops. The remains of a stone boundary wall support this theory and may have once enclosed the agricultural area. There is also an additional smaller breach located elsewhere on the site, its circumstances unknown. By the 21st century, the site had suffered from erosion and off-road vehicle damage, prompting conservation efforts. Today, it is designated as a Scheduled Ancient Monument and remains a valued cultural and landscape feature, symbolising the historical depth and identity of the south-eastern Welsh Valleys. Since then, the site has been greatly modified, restored and landscaped by the council and Cadw since 1984. It now forms part of the Cwmcarn Forest Drive, with ongoing public interest in its archaeology, heritage, and natural setting.

Artefactual evidence from Twmbarlwm Hillfort is relatively limited, primarily due to a lack of large-scale, modern archaeological excavations. Folklore and anecdotal accounts have long surrounded Twmbarlwm, including unverified claims of buried weapons, bones, or treasure. While such stories reflect the hill’s cultural significance, they are not supported by verifiable archaeological evidence. In recent years, aerial photography and limited geophysical survey work have revealed potential subsurface features, including possible roundhouse platforms and ditches. These findings suggest that further excavation could yield more definitive artefactual evidence relating to Iron Age domestic and defensive activity. While the current artefactual record from Twmbarlwm Hillfort is limited and fragmented, the site holds considerable potential for future investigation. With its prominent location, structural features, and historical associations, Twmbarlwm remains an important archaeological site within the landscape of south-east Wales.