1.Ynys-y-Fydlyn is a distinctive promontory but no cross-banks suggesting a defensive function were noted during field work. The neck of the promontory is fractured leaving the seaward end inaccessible, while the landward end is now under forestry and is also largely inaccessible.

David Leighton, RCAHMW, 1994

2. There is a distinct bank cutting across the E side of the island from NE - SW., about 20m long, 0.5m high and 0.75m wide, cut through by a footpath near its NE end. Though artificial it is a rather slight bank and as Frances Lynch has pointed out in an unpublished document: "a rather pointless construction". However it can be seen as part of a 'defence' even if it served only as a token barrier. This part of the island is now separated from the rest of the island (on which there is a single hut circle, NPRN 422209), by a deep unjumpable chasm, though both parts of Ynys y Fydlyn are approachable at low tide. Very unlikely the chasm has formed since the building of the hut or the defensive bank, but a natural arch spanning the gap could have fallen in during this time. The bank would then make more sense as a 'defensive' feature.

John Latham RCAHMW 8 August 2017
Source: Unpublished report for the National Trust, Mynachdy 1991, John Latham.

3.Ynys-y-Fydlyn, as part of Carmel Head, has been monitored as part of the CHERISH project, due to being at risk from natural processes exacerbated by climate change. CHERISH (Climate, Heritage and Environments of Reefs, Islands and Headlands) is an EU-funded Wales-Ireland project (2017-2022) led by the Royal Commission on the Ancient and Historical Monuments of Wales, in partnership with the Discovery Programme: Centre for Archaeology and Innovation Ireland, Aberystwyth University: Department of Geography and Earth Sciences and Geological Survey, Ireland. Work included aerial survey in 2016 and photographic survey in 2018.

H. Genders Boyd, CHERISH, April 2022

4. Summary

This interesting later prehistoric defended coastal islet, essentially a coastal promontory fort, appears to have been misunderstood in the past. New data has been obtained from low-level Royal Commission aerial photography on 18th Oct 2018, 2023 all-Wales 1m LiDAR data and a Royal Commission field visit on 17th September 2024.

The offshore islet, currently accessible at low tide, now stands in two parts but it is likely that a land bridge originally joined the two sections before the progress of coastal erosion. It is most unlikely that there was ever a mainland component to this monument. The two parts of the defended islet currently measure 190m east-west by 55m north-east, and enclose just under 1ha of usable coastal headland. Evidence for up to 15 house platforms has been identified within the fort.

Main structural features: eastern islet

The main defensive feature is a single rampart, 26m long by 5m wide, sited on the southern edge of the inner islet. The rampart runs broadly east-west, and was quarried from upslope. Rather than being a simple ‘dump’ rampart as described by the Gwynedd Archaeological Trust, this is a structural wall whose core is made up from quarried bedrock and beach cobbles retrieved from below the fort. Its core is visible where a path cuts through at the north-east end. A rock buttress below and to the south-east of this rampart, leading up from the beach, can be assumed to be the eroded section of one particular access point up into the fort. The ground climbs steeply above this rampart and apart from some overhanging rock outcrops, the remainder of the interior of this eastern islet appears featureless.

Main structural features: western islet

Access up to the western islet is via a steep but climbable rock gully on the south-east corner. This well-defined gully enters the islet between two natural rock bluffs; indeed the passage of the gully seems to have been artificially improved, with the rock bluffs essentially forming natural inturned bastions of a hillfort gateway. It seems likely that this is an improved gateway feature, perhaps originally linked to the eastern islet and rampart via a now-collapsed rock bridge.

Inside the western islet a number of rock cut platforms can be made out, shelved into the undulating interior of the headland. Previously only one roundhouse has been identified (NPRN 422209) and this survives as a 5m-round (or slightly oval) low turf-covered walled building with an east facing doorway. Although it could be prehistoric, it appears to be distinctly different and better preserved than the surrounding house platforms.

A cluster of around 10 house platforms or ‘hut scoops’ can be seen on Royal Commission aerial photograph AP_2018_5896 from October 2018, as well as on LiDAR, and these are grouped on the more sheltered northern side of the islet. On the ground, between 12-15 terraces and scoops can be made out some linked by or grouped within low walls. The 2018 aerial photographs also show a well-defined scarp-edge bank around the northern rim of the headland.

Thus there is good evidence for a well-settled interior, with a number of house terraces cut into the coastal headland. The interior structures are reminiscent of coastal promontory forts in Pembrokeshire, including Buckspool (The Castle), NPRN 305429, or Sheep Island NPRN 401623.

Visited by Toby Driver and Louise Barker for the Royal Commission, 17th Sept 2024