Nevern castle sits, an earthwork with traces of masonry walls and deep rock cut ditches, on a spur formed by the gorge of the stream; the Gamman, on the north side of the valley of the river Nyfer. It overlooks the church of Nevern and its associated churchyard containing early Christian crosses. It lies less than 2 miles west of the present day town of Newport in north Pembrokeshire and was once centre of the cantref and Medieval lordship of Cemais. In the 12th century the Norman lord Robert FitzMartin and later his son William FitzMartin ruled the barony of Cemais from this castle. The castle was part of a bitter family struggle in the 1190’s between the Lord Rhys, William FitzMartin’s father in law, who had taken the castle from him when he went to fight in the crusade, and his sons. Initially an earth and timber castle circa 1108-1110; it was rebuilt in stone in the late 12th century. Lord Rhys was imprisoned in 1194 by his sons in this castle, probably in the base of one of the two towers whose remains have been uncovered by recent excavations. The castle was deliberately demolished by 1195 and the site left to agriculture. The archaeological remains preserved on this site tell the story of the Norman and Welsh struggle for control of Pembrokeshire during the 12th century.

The existing historical record suggests that the castle was the 11th century site of the local Welsh lord Cuhelyn prior to its capture by Robert FitzMartin in the Anglo-Norman conquest of Pembrokeshire circa 1108/9. FitzMartin created Nevern as the caput for his barony of Cemais, the motte on this site is almost certainly the castle that he established. Subsequently the Welsh recaptured Ceredigion in 1136, following the battle of Crug Mawr; this may have given control of much of northern Pembrokeshire including Nevern to the Welsh, and after 1156 this meant The Lord Rhys. In 1171, after reaching agreement with Henry II, the Lord Rhys was given the rank of Justiciar, allowed to retain his ancestral lands of Deheubarth but required to return all other lands to their Anglo-Norman lords. It is highly likely that soon after 1171 the ownership of the castle had passed to William FitzMartin (Robert’s son) since William married Angharad, the Lord Rhys’s daughter, at some point in the 1170’s. Following the death of Henry II in 1189, in 1191 the Lord Rhys captured Nevern Castle from his son-in-law. Control of the castle then swapped back and forth between the Lord Rhys and sons (Hywel Sais, Grufydd and Maelgwn), with the Lord Rhys being held prisoner in the castle during 1194, before his death in 1197. It is recorded that in 1195 Hywel Sais dismantled Nevern Castle to prevent it falling into Anglo-Norman hands and in 1204 Anglo-Norman forces recaptured north Pembrokeshire including Nevern. It is likely that a new castle and borough had been established in Newport by 1204 and there is no record that Nevern castle was ever rebuilt. Newport Castle was later rebuilt in stone in the mid 13th century.

The historical record suggests the following sequence of control of Nevern Castle and the Barony of Cemais:

Pre 1109 Welsh control under a local leader (Cuhelyn), possibly the site of his llys.
1109-1135 26 years – Anglo-Norman control (Robert FitzMartin). Castle and borough developed. Probably an earth and timber castle constructed. The abbey of St Dogmaels established.
1135-1171 36 years – uncertain, probably predominantly Welsh control, Anglo-Norman control could have returned briefly in the 1150’s.
1171-1191 20 years – Anglo-Norman control (William FitzMartin). The castle was largely rebuilt in stone in this period.