A cropmark was identified on an aerial photograph in 1990 during drought conditions. The photograph was taken by Mary Aris and a copy was deposited in the Gwynedd Historic Environment record (HER PRN 37976 FI file 2013). It revealed a small hilltop enclosure, with hints of internal features, and two concentric banks. The site is located 1 km from the north coast of Anglesey just to the west of the farm of Penyrorsedd in Cemlyn. A geophysical survey was carried out by David Hopewell and John Burman on 08/12/2014 and 09/12/2014. The site was in two fields separated by a wall with a surmounted by a single strand of wire. The survey area was in a pasture field with short grass and there were no obstacles. An area of 120m x 120 m was surveyed.

The morphology of the site at Cemlyn strongly suggests that it is a Roman fortlet. It lies at a height of 34m OD on a hill overlooking the north coast of Anglesey with good views in all directions. It appears to be intervisible with the probable late Roman watchtower on Penbrynyreglwys 3.4km to the west. A detailed evaluation of lines of view was, however, not possible during the survey due to poor visibility.

In the absence of dating evidence, the site cannot be assigned to any particular phase of Roman occupation with certainty. All of the confirmed fortlets in Wales were in use in the first few decades of the occupation and all are on, or close to, the lines of Roman roads. Given the similarity to other first century fortlets there is a strong possibility that it is part of this early network of roads and forts. If this proves to be the case it would be the first military installation from this period to be discovered on the island and would probably indicate the position of a node in the hitherto untraceable road system.

Text edited from Hopewell 2014. Edited by Toby Driver, RCAHMW, Oct 2018.

Reference:

Hopewell, D. 2014. Field Evaluation of Scheduling Proposals: Cemlyn Cropmark. Gwynedd Archaeological Trust, Project No. G2246, Report No. 1220.