It is not known when the St Mellons Church was first constructed however it first appears in historical records in 1254. It has been theorised that during their conquest of Wales, the Normans constructed it as their new church and dedicated it to St Mellonius, the early 4th-century Bishop of Rouen who was purported to have been born in the same area of Wales.
Though the church had been standing since the 13th century, none of the original materials makes up substantial parts of the church as it currently stands. The only parts of the church that remain from its original construction are the base of a high cross in the churchyard and the base of the Baptismal font which was made from parts of a Norman pier. It is implied that church was reconstructed in the 14th century in view of the architecture of the tower and the design of the stained glass windows. Despite this, the majority of the church is pre-English Reformation.
In the 19th century, the church underwent a series of restorations respecting its medieval designs. The renovations of 1858–9 to the main body of the church by George Gilbert Scott were sponsored by Edward Augustus Freeman of Llanrumney Hall. Further work of circa 1869 was by Charles Buckeridge. The chancel was restored in 1875 by Ewan Christian with the tower following in 1910. Some doors were reportedly made from the wood of warships dismantled at Dover after World War I, apparently including HMS Temeraire.
References:Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.