Fragmentary shattered ruins of a great stone-built fortress crown the twin peaks of Deganwy Castle. This was Arx Decantorum, the seat of Maelgwn tyrant of Gwynedd in the sixth century, burnt by lightning in 812 and destroyed by the Saxons in 822 AD (see NPRN 404377). In the late eleventh century this was the seat of Robert of Rhuddlan from which he levied extortion on Gwynedd and from which he rode out to his death. As the Castrum de Gannoc it changed hands, was rebuilt and destroyed throughout the thirteenth century. The visible ruins are those of the great castle, accompanied by a borough, built by Henry III in 1245-50 that was beleaguered for seven years before being systematically destroyed by Llywelyn ab Gruffudd in 1263. Some activity continued at the site and the borough was still active in 1305.
The castle was excavated in 1961-6, when evidence was recovered for a later prehistoric style fortress on the western peak, along with first to third century Roman material.
The main castle court occupied the western crag and enclosed an area about 60m across. It included at least one great round tower and several domestic blocks. The smaller eastern crag was crowned by the irregular Mansel's Tower. The area between the crags was enclosed by great ramparts and walls, with a monumental twin-towered gatehouse on the south-side.
Extensive settlement earthworks to the north and south of the castle (NPRN 400533, 400535) may represent several periods of occupation, including the thirteenth century borough (see NPRN 400533). The name attached to this area, 'the Vardre', suggests that it was at some time a bond settlement associated with a local court.

Sources: RCAHMW Caernarvonshire Inventory I (1956), 152-5
Alcock in the Archaeological Journal 124 (1967), 190-201

John Wiles 27.07.07