Dinas Dinlle, a bivallate hillfort occupying a low hill overlooking Caernarfon Bay, is suffering from coastal erosion. The defences on its western side and part of the interior have been lost, and it is estimated that the fort will be entirely lost within 500 years. Because of this threat, since the mid-1990s the fort has been the subject of numerous studies and investigations. Geophysical surveys revealed roundhouses, walls, enclosures and other structures arranged around trackways and paths in the fort's interior. Wind-blown sand covers the fort's interior, defences and external areas; this started to form in the prehistoric period and continues to accumulate. Following an evaluation in 2019, two area excavations were carried out in 2021 and 2022. Part of a small stone-built roundhouse, c. 6.4m diameter internally, possibly of Late Iron Age date, was excavated in Trench 2. It fell into disuse and was infilled with a midden deposit in the late first/early second century AD. A larger stone-built roundhouse, externally 13.6m diameter, internally 8.6m diameter, was completely excavated in Trench 1. It may have originated in the latest Iron Age, but more likely in the Romano-British period, with occupation continuing into at least the late third century AD and abandonment probably in the early fourth century. An assemblage of Roman pottery, copper alloy artefacts, iron tools and fittings, quernstones and environmental remains were found, all indicative of the domestic nature of the site. There was no evidence for post-Roman occupation of the fort.
McGuinness et al. (Thu,) studied this question.