Historical records suggest that the castle is on the site of the 11th-cenury Llys of Cuhelyn, captured by Robert FitzMartin during the Norman Conquest of Pembrokeshire AD 1108-10. FitzMartin made Nevern the head of his barony of Cemais with the construction of a substantial motte and bailey castle. From 1155 Nevern changed hands between Rhys ap Gruffudd (the Lord Rhys, Prince of Deheubarth) and William FitzMartin (Robert's son) on several occasions. In the 1190s it was also involved in the filial conflict between Lord Rhys and three of his sons (Gruffudd, Maelgwyn and Hywel Sais). The Annales Cambriae record that Hywel Sais deliberately destroyed the castle in 1195 to prevent it falling into Anglo-Norman hands. Destruction at this date is evidenced in the archaeological record and after this date the castle no longer appears in written records.

Nevern is an important rare survival showing the evolution of an earth and timber castle into one of stone and if carried out by Lord Rhys, represents one of the earliest Welsh stone castles.

The castle is situated on a spur formed by the gorge of the River Gamman. It survives as an earthwork with traces of masonry walls and rock cut ditches. Banks and ditches (double on the north and single on the west) enclose the spur in a form that suggests a multivallate Iron Age inland promontory fort, although excavation has not revealed evidence for this origin. Overlying the north-west angle of the rampart is a substantial 8m high motte with the remains of a stone tower; a substantial rock-cut ditch cuts off the eastern end of the bailey to form an inner castle where evidence of an earth and clay bonded stone (slate obtained from the rock cut ditch) curtain wall and tower survive. The main approach and entrance to the castle was on its north side, with evidence for two phases, an earlier looped approach running around the eastern end of the outer rampart and along a sunken roadway in front of the inner rampart. A later direct approach crossed the outer ditch and a postern gate was situated in the southern corner of the bailey.

Excavation has revealed evidence of the early 12th century earth and timber castle that was substantially rebuilt in stone during the mid to later 12th century. The main defences throughout the castles history comprised an earth inner rampart topped with at least three phases of wooden palisade, with the later development of stone towers and an additional thin stone wall along the outer north rampart.

The site is owned by Nevern Community Council and a research project including survey and excavation in partnership with the Community Council and Pembrokeshire Coast National Park have been led by Chris Caple of University of Durham since 2008. RCAHMW has carried out a detailed survey of the castle in support of the project.

Louise Barker, RCAHMW, November 2015

Sources:
Caple, C and Davies, W 2008. Surveys and excavation at Nevern Castle 2005-8. Archaeology in Wales 48, 39-46.
Caple, C 2009 Nevern Castle, Castell Nanlyfer. British Archaeology 109 (Nov/Dec 2009) 28-33
Caple, C 2011 Nevern Castle: Searching for the First Masoary Castle in Wales. Medieval Archaeology, Vol 55 326-333
King, J D C and Perks, J C 1950-51. Castell Nanhfer, Nevern (Pembs). Archaeologia Cambrensis 101, 123-128