HLW (Gw) 11

Transfynydd Basin and Cwm Prysor  

2001  

Outstanding  

Designated  

The Trawsfynydd Basin forms a distinctive topographical unit to the south of Snowdonia, situated between the Rhinog Mountains and the western foothills of the Arenig. The basin floor is at 200m above OD with the east and west sides rising to watershed summits in excess of 500m above OD. The south side is shallower however, with a gap and route out of the basin provided by the River Eden valley. The northen lip of the basin overlooks the Vale of Ffestiniog and Snowdonia which lies beyond this. Cwm Prysor forms a tributary valley on the east side of the basin and affords a natural route up to the watershed below Moel y Slates and beyond, outside the area. This characteristically upland and remote area of Wales, apart from being a historic route corridor, contains well preserved evidence of military control and activities, from the Roman period onwards, as well as a small range of late prehistoric, medieval and later settlement. It is the landscape which inspired the Welsh poet Hedd Wyn to compose his celebrated poetry at the beginning of this century. However, since 1960, the reactor building of the Trawsfynydd nuclear power station, hailed as a masterpiece of planning in its day, has dominated, and to some, spoilt the prospects of the basin floor from all directions. Arguably the most important features of this area are the exceptionally complete Roman military remains, centred on Tomen-y-mur, but also including Dolddinas practice camps and sections of Roman road and tile kilns at Pen-y-stryd. The complex around Tomen-y-mur is unparalleled in Wales and includes the fort itself, fragments of a bath house, an amphitheatre, a parade ground which is overlooked by a mound thought to be the tribunal, a vicus or civilian settlement, a bridge, a road, leats, barrows and so on, in an almost undisturbed setting. The oval embanked amphitheatre is the only one of its kind known to exist at a Roman auxiliary fort in the British Isles. The site has not been excavated, but finds from the complex include nine inscribed stones. To the east lie at least five practice camps at Dolddinas, and to the south alongside the contemporary road are the remains of tile kilns and sections of Sarn Helen, the arterial north-south Roman route through Wales. Tomen-y-mur is cited as one of the courts in the early Welsh Mabinogi tale of Math fab Mathonwy, in which it is known as Mur Castell, and its military significance continues into the medieval period with the construction of the motte (tomen) which now crowns the fort. The Normans had twice, in 1095 and 1114, attacked the stronghold of Gwynedd and built an earthen motte within the Roman fort, probably because its location was still militarily and strategically central in relation to Gwynedd and therefore an easy base from which to mount attacks, with a surviving network of Roman roads coming in from the north, east and south. Castell Prysor, a similar motte in Cwm Prysor, was one of two administrative centres in the medieval commote of Ardudwy, and it has been suggested that the manor of Prysor was specially created as a defensive site to guard a sensitive part of the eastern frontier of Gwynedd, which as far as the princes of Gwynedd were concerned, was their most vulnerable flank. The natural boss of rock in Cwm Prysor was an ideal location on which to build a fortification to halt an invasion from England and Powys. The bailey adjacent to the motte, and apparent foundations for a hall, are possibly unique in Gwynedd. Although the place was deserted by 1284, the general layout of the demesne as it formerly existed around the castle can still be discerned with reasonable clarity from the nature of the ground and various placenames. The area occupied and partly cultivated by resident bondsmen extended down the valley for about 3km, with waste lands to the north, east and south, unoccupied but let for summer grazing. The 1420 Extent shows that there were about twenty free holdings (gafaelion) which would probably have been on the best land near the River Eden to the west. Much of this land was deserted by the 15th century and the subject of much dispute in the next two centuries. Trawsfynydd itself is a characteristic slate quarrying village of more recent origin, which developed in the last century when most of the men worked in the quarries at Blaenau Ffestiniog. However, close to the Roman remains at Tomen-ymur are the remains of Braich Ddu slate quarry, a shallow, dispersed working that produced good coloured slate. It closed in 1868, but some significant features remain, including the rough slab causeway with an interesting bridge. One of the most striking fe a t u res in this area are the re m a i n s of the Bala and Ffestiniog railway running through Cwm Prysor. It was originally built in 1882 to take slate directly from Blaenau Ffestiniog to Birmingham, and between the former and Bala Junction, it had to be carried over no less than 57 bridges and 16 viaducts because of the open, wild character of the terrain. The summit was at the top of Cwm Prysor (where a station was opened in 1902), below which, at Blaen-y-cwm, is a great viaduct of 285m span brick arches on stone piers, after which it follows a route of ledges and sharp curves along the north side of the valley down to Trawsfynydd station before turning north towards Ffestiniog.The line was finally closed in 1961 because of the decision to flood the Tryweryn valley for a reservoir. During the First and Second World Wars there were military barracks at Bronaber (in the vicinity of the present Rhiw Goch village), housing soldiers who trained on the surrounding artillery ranges, the greater part of which lie to the east, outside the area described here. It is perhaps ironic that the Welsh poet Hedd Wyn (Ellis Humphrey Evans) lived at Ysgwrn in Cwm Prysor and was killed in the trenches of the First World War and posthumously awarded the Chair at the Birkenhead Eisteddfod in 1917.The area had clearly provided the inspirational source for much of his writing. The Maentwrog hydro-electric power station (currently outside the area described here) was built near Trawsfynydd in 1928, which led to the creation of an artificial lake here, and in the 1960s the nuclear power station was added and the lake extended. The latter building was designed by the architect Sir Basil Spence and the immediately surrounding area landscaped by Sylvia Crowe. Power generation has recently ceased however, as the station came to the end of its useful life.