1. The monastery on Priestholm is thought to have been an early medieval foundation. It was associated with Penmon Priory (NPRN 95543), itself an Augustinian house when it was granted to the Prior and Cannons of Priestholm in 1237. Following this the Prior of Priestholm shifted to Penmon. There are remains of a church, notably the twelfth century tower, and other monastic buildings, ranged within and about a walled enclosure. The church tower stands central to a ruinous building complex comprising the footings of the Nave to the west, the Chancel to the east and a transept to the south, now occupied by a cottage.

2. Description from 1937 Royal Commission Anglesey Inventory (p. 142):
'The Tower (8 3/4 ft square) is one of two stages with a squat pyramidal stone roof. On the E wall is visible the roof line of the early chancel with that of the 13th century above. The crossing has original round arches in the E and W walls both built of rubble with chamfered imposts. Above the centre of the E arch a Roman box tile is built in. In the S wall is an opening with a roughly-constructed semi-circular arch cutting through the reveals f a narrow round-headed window; the arch was inserted at a later date to give access to a transept, the site of which is now occupied by a modern cottage. The upper stage is marked by a plain projecting string course and has original round-headed windows in each wall, those to the S and W of two lights with the shafts missing. The floors have disappeared.'


3. The ruins of the church were selected for survey as a designated baseline study site for the EU-funded CHERISH Project (2017-2021) due to their general inaccessibility, their protected status and for the purposes of monitoring the structures following conservation works to the tower circa. 2009.

An initial visit was made to the island on 21st June 2018 by staff from the Royal Commission's CHERISH Project in the company of a Cadw Field Monument Warden (J. Spencer) and Dr Jonathan Green, Liverpool University, the current Licence Holder. The church tower and associated buildings stand in a clearing in dense elder woodland. The approaches are overgrown, largely obscuring the wider remains of the monastic enclosures and walls planned by Royal Commission staff for the 1937 inventory when the island vegetation was open, grazed pasture. The immediate environs of the buildings are more clear, but still surrounded by waist-high vegetation which was cut and cleared (with permission) on arrival. The walls of the church and cottage on the west and south sides are grown with ivy. The main survey work on this visit was to complete a new laser scan survey of the church for Cadw and the CHERISH Project.

A second visit was carried out on 26th November 2018 with the purpose of undertaking drone photogrammetry of the top of the tower and other upper surfaces of the ruins which were inaccessible to the earlier ground-based laser scanning, completing the baseline monitoring survey for the standing structures. A rapid record was also obtained of the standing buildings:

Tower: East Wall; East arch: 2.73m high x 1.55m. Possible Roman box flue tile in wall above arch. Traces of pitched roof fitting above. North wall; No arch. Small window in upper storey. Protruding masonry low down on NW corner suggesting intention to link to additional wall or structure. West wall; Arch, 2.5m high x 1.76m wide. Blocked. Small putlog hole midway up wall below pitched roof fitting. Inside tower: Arch in south wall roughly blocked with masonry, preserving smaller narrow inner door 1.14m wide within blocking. Arch in W wall neatly blocked with slight recess. A small pile of numbered, dressed stone has been stored in the inner NW angle of the tower.

Other external buildings. Ruined cottage (site of transept) on south side of tower. Blocked archway into tower on south wall, with small Romanesque arch above. Plaster line high up on tower of shows line of former pitched roof line. East and West cottage walls standing 1.8m-1.9m high but heavily grown with ivy with much loose stone at upper levels. East wall has simple central window. The south wall of the cottage preserves a fireplace and chimney breast. The fireplace opening measures 0.83m x. 0.90m with a large lintel stone of contrasting red sandstone. Floor littered with tumbled masonry and roof slates.

Room adjoining on west side of cottage, accessed through door in west wall. Walls heavily ivy grown, standing internally c. 2m high. Floors infilled with rubble throughout.

Wall footings of the chancel on the E side of the tower. Walls standing 6-8 courses high, generally surviving 0.6m - 0.7m high. Infilled with tumbled rubble. Vegetation cleared here during summer 2018 visit with obvious benefits to the visibility of the standing structures.


T. Driver, D. Hunt, L. Barker, RCAHMW/CHERISH Project, Nov 2018

References:

Driver, T. 2023. Puffin Island or Ynys Seiriol: Archaeological investigation of the church, monastic settlement and wider landscape for the CHERISH Project, 2017-18. CHERISH Report No. CH-RCAHMW 10. Unpublished Report; RCAHMW.

Hughes, H. 1901. Ynys Seiriol. Archaeologia Cambrensis Vol. I. Sixth Series. 85-108 https://journals.library.wales/view/4718179/4718621/123#?xywh=-941%2C525%2C4198%2C2021

RCAHMW, 1937. An Inventory of the Ancient Monuments in Anglesey, London: HMSO