According to Sedding, the lower part of the nave N wall, the N and S walls of the chancel, the walls of both transepts, the inner arches of the original round-headed windows and much of a semicircular arch of the chancel remain from the Norman church. Pevsner also noticed traces of round-headed arches in the transepts. The only remains of Romanesque sculpture are the font and the two panels in the outside wall of the chancel. The figure panels date from the third quarter of the 11thc, the early Norman or Saxo-Norman overlap period. The font is of the first half of the 12thc.

The monastery of St Stephen was established long before the Conquest, and the surrounding township was known as Lan-stefan-ton, or Launceston. The Norman Earls of Cornwall acquired the ford of Dunkwed on the neighbouring hilltop and induced the townspeople to move, transferring the name of Launceston to Dunkwed. Early in the 12thc, the monastery itself was moved nearer the Norman town, and a new priory was built in the river valley between the two hills. The old church of St. Stephen was partially rebuilt to serve as a parish church, and rededicated in 1259. It remained the mother church of numerous chapels throughout the medieval period, including Tremaine, Egloskerry, Tresmeer, Laneast and two churches in Launceston: St Thomas and St Mary Magdalene.