Old maps and plans of the town of Llanelli show an ancient fortification on the site that is now bounded by the buildings that are known today as ‘The Metropolitan’, ‘Castle Field’, ‘Le Caprice’ (Castle Buildings) and Pencastell. Past historians have referred to this site as being Roman or Norman in origin. Early Ordnance Survey maps name the site as ‘Ancient Camp’ or ‘Pen-y-Castell’.
Before the construction of Castle Buildings at the end of nineteenth century the site is outlined as a square or rectangular shaped earthwork with rounded corners. The earth work was approximately fifty metres square, lying today on the mound that is John Street and was approximately sixty metres from the now culverted river Lliedi.
One early plan of the site clearly shows it as the classic ‘playing card’ shape typical of a small fortlet or ‘practise camp’ constructed by the Roman army when in hostile territory. On arrival at a strategic position such as a spur or platform overlooking a river-plain, the soldiers would dig '' V '' shaped trenches, and with the spoils they would raise earth ramparts topped with a wooden palisade of sharpened stakes, the entire structure forming a rectangle or square.
Given the close proximity of this site to the major Roman fort at Loughor, there is strong evidence that this site was indeed a Roman fort or camp. Comparative Roman fortlets and camps of this type have been identified at Trawsfynydd, Tomen y Mur, Llanfaircaereinion and much closer to Llanelli, at Gorseinon.
The first detailed reference to Llanelli’s Roman site appears in the ‘The history of the Llanelly Parish Church’ by the Victorian historian Arthur Mee (1888), he attributes the site as being Roman, stating...
Eighteen hundred years ago Llanelly was a Roman out-post. The Legionnaires, penetrating ever westward, arrived at length at Loughor. There they founded a settlement, and spanning the river with a bridge of wood, pushed on to Llanelly. This was their terminus in South Carmarthenshire. Elsewhere in the county they left traces of their presence in the shape of roads and other works, and still more enduring monuments of etymology. But at Llanelly a square green camp alone remained until the present decade to tell of the place as known to the Romans.
John Innes the author of ‘Old Llanelly’ witnessed the removal of this earthwork and wrote that
‘The Old Castle was the square mound where John Street now stands and nothing else. There were no foundations or buildings of any kind’. Further evidence to support the possibility of the Roman occupation of Llanelli is the cluster of coin finds in and around the town.
A detailed archaeological survey and investigation of the Pen-y-Castell site is required to prove conclusively that the site is of Roman origin. But from existing cartographical evidence, there may well have been a temporary Roman marching camp on the site that was destroyed or built over in the late 19th century. From this temporary fort the Romans would have guarded a nearby fording at the river Lliedi.