New visitors to ancient places: the use and re-use of an Iron Age ‘banjo’ enclosure at Radyr, Cardiff

Excavation by Cotswold Archaeology during the wet winter of 2019–20 found evidence for a previously undiscovered hilltop enclosure at Radyr, north-west of Cardiff. Finds from the site were sparse, and its long history was only revealed through a programme of radiocarbon dating. Despite the extremely challenging ground conditions, our archaeologists were able to recover valuable evidence for this Iron Age site, and its re-use in the Roman and early medieval periods.

Challenging ground conditions, looking south-east from the site over the Taf valley and beyond
Challenging ground conditions, looking south-east from the site over the Taf valley and beyond

The enclosure occupied a hillside plateau, with far-reaching views to the south-east down the Taf valley to Cardiff and across the Severn Estuary to Somerset. In its original form the enclosure comprised an outer ditch that was 120m long and 85m wide, within which an inner ditch enclosed a post-built roundhouse and a few pits. These remains were radiocarbon dated to the Early Iron Age (the dates spanning 742–398 cal. BC) and produced a small assemblage of broadly dateable Iron Age pottery.

Roundhouse and the view down towards Cardiff
Roundhouse and the view down towards Cardiff

Later, paired ditches were added to the north-east of the enclosure to create an ‘antennae-like’ entrance, which turned to run sharply downslope. This later form of the enclosure falls into a type known as ‘banjo enclosures’, a form widely known in southern Britain through cropmarks and earthworks but rarely investigated by excavation. These are often thought to date to the Middle to Late Iron Age, but certainty is hampered by a general lack of excavated examples, and the enclosure at Radyr, which originated in the Early Iron Age, lacked clear evidence for its use beyond the Middle Iron Age.

Plan of the Middle Iron Age 'banjo enclsoure'
Plan of the Middle Iron Age ‘banjo enclosure’

Typically, no animal bone had survived the acidic soils of the site that are common in this region, but the form of the enclosure with its antennae ditches leading to the valley floor suggests an association with livestock farming – cattle might have been corralled in the outer enclosure in winter before being driven to summer grazing alongside the Taf, suggesting that the enclosure may have been seasonally occupied by a herder or herders.

Plan showing Roman features
Plan showing Roman features

Later still, the Iron Age earthworks were re-used when an adjacent enclosure was laid out in Roman times. This was probably for a farmstead associated with pastoral farming, although again occupation may have been seasonal. The Roman farmstead used pottery produced during the 2nd to 4th centuries AD and produced two radiocarbon dates spanning cal. AD 27–225, broadly within the Early to Mid Roman period.

Another significant discovery was that several post-Roman features were distributed around the edges of the former Iron Age enclosure. These features lacked dateable finds and were only identified as being of early medieval date by radiocarbon dating. One contained iron slag and may have been the remains of an iron smelting furnace; it produced a radiocarbon date in the later 7th to early 9th centuries AD. The remains of two other possible furnaces (one perhaps a crop-processing oven) produced similar radiocarbon dates, and fourth possible furnace was probably of the same date based on morphological comparison. A small pit with a burnt fill produced an earlier radiocarbon date within the early 5th to mid 6th centuries AD. Together, these indicate re-use of the Iron Age earthworks in the post-Roman period for purposes that included iron smelting and possibly crop-processing. The smelting undertaken at Radyr used tapping, a technique where the slag is allowed to run out of the furnace. This technology is currently understood to have been used during the Roman and later early medieval (after the 9th/10th centuries AD) periods; the findings from this project raise the possibility that tapping was also in use between the later 7th to early 9th centuries.

Later remains included a medieval crop-processing oven, radiocarbon-dated to the later 11th to early 13th centuries and found to contain the charred remains of spelt wheat and barley, with some free-threshing wheat and rye. The oven would have been built at a field edge to partially dry freshly harvested crops before storage, perhaps within a farm, village or monastery.

Jonathan Hart

The work, undertaken in advance of residential development (part of Plasdŵr ‘Garden City’), was funded by Redrow Homes.

View of the site, archaeologist excavating the enclosure ditch in the foreground
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