The church of St. Stephen and St Tathan was built in the 13th century, probably using stones from the ruins of the Roman fort Venta Silurum. Although it is known, that in Caerwent was a church also before the Norman period, there is no evidence that it was in place of a medieval building. In the fifteenth century St. Stephen’s church was rebuilt and enlarged, and the porch and tower were added to the existing building. Subsequent changes were made during the Reformation period, when lateral, southern chapels were removed. In the years 1893-1894 and again in the years 1910-1912 the church was restored. During the last restaurant a small southern aisle was also erected. In 1968, the sacristy was added on the south side of the chancel.
The church consists of a rectangular nave and also a rectangular chancel, which is the oldest element of the building. In the southern wall of the chancel there are three arches from the thirteenth century, which probably led to the no longer existing south aisle at the choir. The chancel is ended from the east by a straight wall with two lancet windows and corner buttresses. Two arches in the south wall of the nave originally led to side chapels, probably destroyed in the 16th century. Today their place is occupied by the neo-gothic small aisle. In the fifteenth century, a three-storey porch was added to the nave from the north and a tower from the west. The church is in possession of a few Roman monuments, including the altar dedicated to the Mars god, dated 152 AD.
Webpage britishlistedbuildings.co.uk, Church of St Stephen and St Tathan (Tatheus), A Grade II Listed Building in Caerwent, Monmouthshire.