According to tradition, the first temple on the banks of the Rumney River in Llanedeyrn was founded in the sixth century by Saint Edeyrn. In the twelfth century, the Normans erected a new church, which they made a chapel of ease subject to the church of St. Mary in Cardiff. In the 12th century it was declared the property of the Tewkesbury Abbey, but was returned to the Llandaff bishops in 1236, when it became a separate parish. At the turn of the fifteenth and sixteenth century, the church was rebuilt, among others, new windows in the perpendicular gothic style and a tower were added. The Victorian restoration of the building was carried out in 1888.
The church received a rectangular, elongated nave and a slightly lower, also rectangular chancel on the eastern side, having the same width. The original windows of the church were very narrow openings, almost slits. The entrance was in the western part of the south wall. Another entrance portal for the priest was located in the southern wall of the presbytery.
A four-sided tower was added to the western side of the church at the turn of the 15th and 16th centuries, slightly embedded in the nave. The entrance portal on its west side was placed and it was crowned with a battlement. On the north side, it received a small projection in the wall with a staircase. An even shallower protrusion in the wall was placed on the northern side of the nave, in order to place inside the stairs to the rood screen loft. The rood screen, probably of wooden construction in the Middle Ages, separated the secular part of the church from the priestly part.
The southern entrance to the nave of the church was preceded by a vaulted porch, probably built in the 14th century. Some of the original church windows in the late Gothic period were transformed into large pointed windows filled with three-light tracery and two-light windows topped with trefoils.
Salter M., The old parish churches of Gwent, Glamorgan & Gower, Malvern 2002.
Website britishlistedbuildings.co.uk, Church of St Edeyrn. A Grade II Listed Building in Old St. Mellons (Hen Laneirwg), Cardiff.