The blunt northern promontory of Ramsey Island, Trwyn Sion Owen, is crossed by two straight, parallel SW/NE ditches apparently defining the remains of an Iron Age coastal promontory fort. The outermost, southerly, ditch straddles the landward neck of the promontory and is 119m long, approx. 5m broad, broken by a simple gateway 12m wide with rounded ditch terminals towards its eastern end. This encloses 1.3 hectares of the coastal promontory. Some 55m to the north is a second SW/NE ditch measuring approx. 128m which crosses the interior of the fort and serves to define a smaller extension to the promontory as a distinct innermost enclosure some 0.4 hectares in extent.

This is the first and only coastal promontory fort identified on Ramsey Island, in contrast to the profusion of such monuments around the Pembrokeshire mainland coast. However it is readily paralleled by South Castle promontory fort (NPRN 305371) on Skomer Island which is almost identical in form, with one or possibly two straight ramparts cutting off a promontory - the outer defence having a single simple entrance gap - and in terms of its isolation on the wider island.

The features have been digitally mapped and updated from 0.25m Lidar as part of the CHERISH Project.

D. Hunt 01/02/2018; T. Driver 22/03/2018

? Crown: CHERISH PROJECT 2017. Produced with EU funds through the Ireland Wales Co-operation Programme 2014-2020.