Dinas Dinlle hillfort is a roughly oval defended enclosure, set on the summit of a drumlin. It measures about 150m north-south by 110m and is defined by double ramparts with an intermediate ditch; there is an entrance in the south east. The enclosure has suffered considerable coastal erosion on the west side and from the beach below, the original ground surface beneath the Iron Age ramparts along with other details are clearly visible in the eroded cross-section. Within the eastern part of the interior are traces of circular or rectangular structures or enclosures, one being a possible sepulchral mound or alternatively a Roman pharos or lighthouse, similar to one to the north on Caer y Twr, Holyhead Mountain (nprn 308080).
Casual finds, including Roman coins of A.D. 253 to 296, an intaglio and a sherd of black burnished ware of the second or third centuries, indicate occupation in the Roman period.
A World War Two Seagull Trench (nprn 270526) has been built in the lower north-facing ramparts of the fort.
RCAHMW, 12 July 2009.
Low light aerial reconnaissance over Dinas Dinlle hillfort on 10th December 2012 provided the opportunity to gather detailed new imagery of the interior of this interesting hillfort. Detail shown includes clarification of the prominent structured mound, postulated as a potential Bronze Age barrow or footing for a Roman pharos, as well as the polygonal enclosure or pen alongside it. This was suggested as a pen or golf tee in the Muckle Partnership’s 2004 survey for the National Trust, but the new photographs show it to have a straight side on the north and to be built against the rampart rather than forming part of it, standing as a discrete polygonal enclosure, adding to the information shown on the original plan. The two linear breaks of slope identified on the survey in the central part of the fort have the appearance of regular terracing. The photographs also show up low banks and a potential platform against the southern inner rampart, not marked on the existing survey.
T. Driver, RCAHMW, 2013.