Llanfihangel-Talyllyn is a very small village set in a historic parish of the same name. Llanfihangel-Talyllyn parish is now part of the community of Llangors. It is situated approximately five and a half miles south east of Brecon. The name Llanfihangel-Talyllyn 'signifies the church of St Casten (or Casteu) at the end (or edge) of the lake and incorporates a dedication that is unique. The earlier forms of the name are various. In 1643, it was recognisable if misspelt as Llangastey Talyllym, and before this in 1513 it was Llangasten. The year after Henry VII's accession the church was termed Sci Castani juxta mar?, while in 1321/2 it was linked to neighbouring Llan-y-wern as the [lands of] Londeworne, altera Costinio. The origin of the church as an early medieval foundation seems incontestable, though it is only the obscure dedication that is convincing. There is however no evidence that a settlement developed around the site, either before the Conquest or during the Middle Ages. The earliest available maps ? from the beginning of the 19th century ? show the church as a solitary structure on the edge of the lake.
The church (NPRN 154425) was 'built in the period 1848-56 in Gothic Revival Early English style to designs on J.L.Pearson, replacing a medieval church on the same site. This formed part of the extensive redevelopment of the Treberfedd Estate following its purchase in the 1840s by Robert Raikes who had been strongly influenced by the Oxford Movement at University and had become a committed Tractarian, principles strongly reflected in the building which features an almost complete Tractarian interior. Pearson was also responsible for the neighbouring school (NPRN 25958) as well as Treberfedd mansion (NPRN 16280).'
Sources: Clwyd Powys Archaeological Trust Historic Settlements Survey of Llanfihangel Tal-y-Llyn, reference number 15962; NPRN 154425 and CADW site description of St Gastayn's church.
RCAHMW, 3rd September 2018.