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Castell Prysor

Also known as, or recorded in historical documents as;
Cwm Prysor

In the community of Trawsfynydd.
In the historic county of Merioneth.
Modern authority of Gwynedd.
Preserved county of Gwynedd.

OS Map Grid Reference: SH75783687
Latitude 52.91482° Longitude -3.84877°

Castell Prysor has been described as a Timber Castle although is doubtful that it was such, and also as a probable Masonry Castle, and also as a probable Palace.

There are earthwork remains.

This site is a scheduled monument protected by law.


The medieval castle mound known as Castell Prysor is formed from an outcrop upon a spur projecting from the hillside above the Prysor valley. There are ruins of several buildings and terraces and enclosures, to the west and east. This is thought to have been a princely court, or llys. A later building (NPRN 28274) occupies an earlier building platform. This is one of several instances in Merioneth where an apparently unfortified mansion or court is associated with a castle mound, for example Crogen (NPRN 306558) and Rug (NPRN 306598). At Aber in Caernarvonshire a thirteenth century court (NPRN 309171) was excavated at the foot of a castle mount (NPRN 95692). A natural rock boss has been formed into a high steep sided mound by the addition of a mass of stones set in clay, retained by a massive spiralling wall. The resulting mound is in the region of 40-50m across and 15-25m high, with a level summit 8.0-13m across. Pennant noted traces of a round tower in the late eighteenth century (Tours ii, 111-12). The castle mound has no certain outworks. Pennant's notice of 'many Roman coins & urns' being found here may be no more than a figure of speach. (Coflein–John Wiles, RCAHMW, 09.07.07)

This natural boss of rock is strengthened and topped by a stone mound which was originally revetted with dry walling, now badly ruined. Edward I wrote a letter from here on 1 July 1284, but it is obviously an earlier Welsh castle. (Lynch, 1995)

A motte and bailey with the foundations of rectangular structures and enclosures NE and W of the motte. The top of the motte stands some 9 m above the level of the bailey, and is 12 m in diameter. The top has been severely damaged by trenches dug across; the principal trench is 6 m across and nearly 2 m deep. The body of the motte is mainly of stone, and revetted stonework is still visible on the sides of the motte, although blackthorn obscures much of this work. The bailey also makes use of natural outcrops of rock, and is defended on the W by a bank 3 m wide and 0.6 m high. There is a small, rock-cut pool in the SW corner of the bailey. (Scheduling Report)

The site of Prysor castle lies high in a steep valley controlling the route from Bala to Tremadog. It has no known history before King Edward I stayed there while surveying his new lands in Wales after the fall of Prince Llywelyn ap Gruffydd (d.1282). That the castle does not appear again in the written record would suggest that the king found his sojourn here uncomfortable and the upkeep of this isolated fortress was considered no longer necessary. We have no idea who built the castle, other than the suggestion that it was a predecessor of Prince Llywelyn.
The ruins consist of a large pile of stones, often wrongly described as a motte. An old print shows that this was once a stone tower which has now collapsed in on itself. Towards the rising hillside was a weak bailey, in which there are the remains of buried portions of what appears to be a hall block, unless it was a later farm. (Remfry 2016 >]

This may well have been a clay bonded round masonry tower, probably of C13 date. The existence of an earlier castle, or high status site, here is absent but, by analogue, it is not reasonable to think there was some earlier occupation although the form of residence is unknown.
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This record last updated 06/07/2016 19:00:13