FitzOsbern had been granted the Lordship of Striguil by his second cousin King William in gratitude for his support in the Norman conquest of England, and was responsible for starting the building of a new castle overlooking the River Wye on the border with the kingdoms of Wales.

At the same time he established a nearby monastic cell, so as to collect rent from the lands within Gwent which he had granted to his home Priory of Cormeilles in Normandy.

By the early 12th century, the monastic establishment, on a ridge overlooking the river about 300 metres from the castle, had the status of an alien priory in its own right,[1] though it probably never held more than about 12 monks.

Accommodation was built on the south side of the church, in the 13th century,[1] and the first vicar appointed by authority of the king, John de Hemmyngburg, is recorded in 1348.

The original Priory Church was built in local yellow Triassic sandstone, with a long vaulted nave, massive piers, and a notably ornamented west entrance doorway with zigzag and lozenge patterns, dating from the early 12th century.

In 1841, through the influence of Edward Copleston, Bishop of Llandaff, who lived locally, the aisles were removed, and the eastern end, crossing and transepts were rebuilt.