Blog - A new survey of Puffin Island - Toby Driver Senior Investigator (RCAHMW)

Puffin Island or Ynys Seiriol/Priestholm rises in a steep ridge of limestone off the eastern coast of Anglesey in north Wales. This magical, privately owned island is home to protected seabirds, principally cormorants, and the ruins of an early medieval monastery. No public landing is allowed without the prior permission of the landowner.

Puffin Island from the air, June 2019

Puffin Island from the air, June 2019

The monastery of Priestholm, an early medieval foundation of which the listed and scheduled tower of the Augustinian priory church still stands proud on the island’s skyline, has long attracted visitors. In 1868 Herford Hopps carried out a basic survey of the buildings and discovered numerous skeletons around the church where rabbits had disturbed the bones. Harold Hughes returned in the final years of the nineteenth century to carry out more accurate surveys of the buildings and to continue with his own excavations, finding remains of an early shrine pre-dating the church tower. The Royal Commission first visited in 1929 to survey the island for their 1937 Anglesey Inventory. The only other substantial building on the island is the listed, ruined 19th century Telegraph station at the north-east point.

In modern times the island and ruins had become overgrown and lacked a modern survey. Therefore Puffin Island was selected as a new study site for the EU-funded CHERISH Project due to its general inaccessibility, the protected status of the buildings and to enable new, highly detailed surveys of the structures to be made to monitor future change and erosion. The CHERISH ‘toolkit’ approach meant that the island would be completely surveyed from the air, on the ground and from the sea.

In 2017 CHERISH commissioned new airborne laser scanning (‘LiDAR) of the entire island. The highly accurate laser penetrates the woodland canopy allowing trees and scrub vegetation to be digitally ‘stripped away’ in a computer. Using this technique we were able to map previously hidden fields, buildings and a new promontory enclosure to build a virtual view of the entire island.

Spectacular 3D LiDAR views of Puffin Island with and without its woodland vegetation.

Spectacular 3D LiDAR views of Puffin Island with and without its woodland vegetation.

Remote sensing can only tell part of the story. In June 2018 CHERISH and Cadw staff accompanied seabird specialist Dr Jonathan Green out to Puffin Island in something resembling a ‘Famous 5’ adventure, beginning with a boat landing among basking seals on the western beach. Negotiating chest-deep grass and brambles and crawling under branches of low trees whilst carrying heavy survey equipment, we reached the peace and solitude of the 800 year old church. The limestone Romanesque tower looked quite continental in the June sun. Seagull chicks looked on as we laser scanned the tower.

Later that summer the Geological Survey of Ireland carried out marine bathymetry along the east Anglesey coast, monitoring wrecks and mapping the inshore island waters. We returned in decidedly colder weather in November 2018 to fly a drone over the tower to gather 3D photos of the parts the laser scanner couldn’t reach.

The new surveys generated state-of-the-art 3D records of the medieval priory church and associated structures, allowing any future change to be measured to within a few millimetres. The marine survey data has been linked to the LiDAR to produce a remarkable seamless onshore/offshore 3D map of the entire island. The current lockdown and a break from active fieldwork has provided the opportunity to write up the various surveys into a substantial archive report, which will be made available during 2020.

3D drone photogrammetry of the church tower

3D drone photogrammetry of the church tower

The CHERISH Team hope to return to Puffin Island in 2021 to make a final monitoring visit of the medieval ruins, and to savour the peace and isolation on this wilderness island one last time.

See our online records for Puffin Island here:

Find out more here