NAR SH46NE7

Castell Bryn Gwyn is a near circular earthwork enclosure defined by a massive rampart that remains up to 2.6m high, with an internal area in the region of 52-56m across. There is little trace on the ground of a ditch and early observers, misled by irregularities in the rampart, identified this as a Roman amphitheatre.
Excavations in 1959-60 demonstrated that the monument had originated as a late Neolithic ritual henge enclosure or similar. It had later been adapted as a defensible circuit, presumably enclosing a settlement. This reuse probably occurred in the later Prehistoric period and its latest phase is associated with Roman pottery of the late first century AD.
The primary Neolithic phase had a 5.2m wide stony bank with a 2.3m wide berm separating it from a broad flat-bottomed external ditch, 1.9m wide and up to 9.8m wide. There was at least one entrance, facing south-west. The ditch had partly silted up and the bank had weathered, when the bank was extended forward into a 9.0m wide rampart, revetted by a dry stone wall and fronted by a relatively insubstantial ditch. Finally the rampart was again extended to a width of 11m with a timber revetment and a new ditch was dug, 5.5m wide and 3.6m deep. The south-west entrance was blocked at this time and a Roman pottery sherd was recovered from the blocking.
Trenching in the interior identified some features, although these could not be resolved into coherent structures and produced no dating evidence.

Sources: RCAHM Anglesey Inventory (1937), 105
Wainwright in Archaeologia Cambrensis 111 (1962), 25-58
Lynch 'Prehistoric Anglesey' (1970), 65-7

John Wiles 09.08.07