The original chapel in the place of the later church in Rhos on Sea (Llandrillo yn Rhôs), was erected in the 13th century. It was built by Ednyfed Fycha, the seneschal of the Welsh kingdom of Gwynedd, and was first mentioned in the documents in 1254. In the fifteenth and the sixteenth century century it was rebuilt and enlarged into the form of the present church. In 1552, a tower was added. Further modifications were introduced in the 17th centuries, and a thorough Victorian renovation was carried out in the 19th century. The church was erected on a hill and whitewashed, to serve as a landmark for sailors at sea. Probably because of the proximity of the sea on the tower, a smaller observation turret was added, to alert the local population in the event of pirate attack, being the plague of the seventeenth century.
The church was situated on a high hill surrounded by a cemetery. In the 15th century it consisted of a rectangular nave without a separated externally chancel. In the 16th century, a southern nave of equal length and the same shape as the previous one was added, and a four-sided tower on the west side of the older nave. Porches have been added to both the southern and northern naves. The walls of the tower were 1.4 meters thick at the level of the battered plinth. It was topped with a breastwork mounted on a cornice and provided with a battlement with characteristic, stepped merlons, typical of many Irish churches.
The oldest part of the present church is today the northern aisle, in the northern wall of which two bricked up arcades and a pointed portal are visible, probably the remains of an older chapel. The remaining elements of the church come from the late medieval period, but were rebuilt during the renovation in the nineteenth century. Inside, a font from the 13th century has been preserved.
Salter M., The old parish churches of North Wales, Malvern 1993.
The Royal Commission on The Ancient and Historical Monuments and Constructions in Wales and Monmouthshire. An Inventory of the Ancient and Historical Monuments in Wales and Monmouthshire, IV County of Denbigh, London 1914.
Website britishlistedbuildings.co.uk, Church of St Trillo A Grade II Listed Building in Rhos-on-Sea, Conwy.