1. St Tudwal's is a small island, only some 430m by 220m, lying off the south coast of the Llyn peninsula. The island was the setting for a monastic settlement from at least the thirteenth century (NPRN 401811). There are records of an Augustinian priory between 1291 and 1509-11. The island is known to have been farmed in the eighteenth century and the former chapel may have originated at this time (NPRN 97198). Plough cultivation ridges cover much of the summit of the island. Traces of an extensive networks of paths represent a monastic garden associated with a short lived monastic revival in 1886-7 (NPRN 401812).
Excavations on the Priory site in 1959-63 produced Roman material, tentatively associated with a timber structures.
Source: RCAHMW Caernarvonshire Inventory III (1964), 48-50
John Wiles, RCAHMW, 01.08.2007.

2. A stone-built fish trap (NPRN 33027) was recorded off the northern tip of the island during RCAHMW aerial reconnaissance on 23rd June 2015.
T. Driver, RCAHMW, 2016.

3. St Tudwal's East is a study site within the EU-funded Ireland Wales CHERISH Project 2017-2020.

New LiDAR survey of St Tudwal's East. In February 2017, Bluesky, a company specialising in the acquisition of aerial survey data, was commissioned by the CHERISH Project to collect 0.25m ?leaves-off? (winter conditions with low vegetation and bare trees) LiDAR (airborne laser scanning) data of six Welsh islands at low tide. This included a new survey of St Tudwal's East, allowing its archaeology to be analysed and mapped to a high degree of accuracy. Bluesky flew from its East Midlands base and collected the data using its Teledyne Optech Galaxy LiDAR system on 24 February. The processed data is archived with the Royal Commission (Driver and Hunt 2018).

Reference:

Driver, T. and Hunt, D. 2018. The White Ribbon Zone. RICS Land Journal. February/March 2018. pp. 22-3