Church of St. Glies in Gileston was probably founded in the 12th century, from this period comes its nave. In the thirteenth or the fourteenth century, it was enlarged by a chancel, and in the fifteenth century, it was thoroughly reconstructed. The roof, windows and the porch were added. The church is dedicated to Saint Glies, although its dedication may also come from the local Giles family. A thorough renovation of the building was carried out in 1883, perhaps from this period the western turret comes from.
At the end of the Middle Ages, the church consisted of a rectangular in plan nave, also rectangular, but narrower and lower chancel on the eastern side, and a porch in front of the southern entrance. Originally, the building was illuminated by small, narrow windows closed with trefoils or ogival arches. In the 15th century, some of them were replaced with larger two-light windows with openings topped with cinquefoils, set under simple frames.
The church retained the layout obtained at the end of the Middle Ages, enlarged in the western part by a small tower embedded in the nave. The southern, two-light windows in the nave and easter window of the chancel come from the end of the 15th or early 16th century, and several older openings topped with trefoils have also survived. The most valuable element of the church is the door located in the southern porch. They come from the years 1450-1480 and have six carved coats of arms and original medieval hinges. The coats of arms represent the local families: the Walshes of Llandough, the Umfravilles of Penmark, Giles, Fleming, and Cradocks.
Salter M., The old parish churches of Gwent, Glamorgan & Gower, Wolverhampton 2002.
Website britishlistedbuildings.co.uk, Church of St Giles A Grade II Listed Building in St. Athan (Sain Tathan), Vale of Glamorgan.
Website coflein.gov.uk, St Glies church, Gileston