The castle must have undergone almost a rebuilding in the Decorated period. The Norman architect evidently treated the whole inner ward as a shell keep. His successors added part of Mortham Tower, and the Decorated artist, more ambitious, raised the round tower as a keep, added—probably rebuilding—the hall, and completed Mortham Tower, and strengthened or restored the curtain in various places. Here, as was much the practice in the North, the round-headed arch and the flat lintel were largely employed in the Decorated period. The general style of the work is much to be admired. Strong, sound, massive, very plain, of excellent execution, it is in admirable taste, and in good keeping with a military structure. The keep, though not one of the largest, is one of the finest round towers in England. Its proportions are good, its materials of proper size and rich colour, and its very plainness is indicative of strength. There is but little Perpendicular work; probably it was of a lighter character, and has fallen and been removed. Whatever may be regarded as the value of the material evidence of its earthworks, the notion of Bernard Castle occupying the site of an earlier stronghold is unsupported by records. The present town is thought to have risen on the fall of Marwood, a place the very site of which is now forgotten; neither is it a parish, being included in the vast parish of Gainford, the church of which is eight miles distant. From Domesday no aid is to be derived, seeing that this valuable record does not include Durham, nor is there any mention of either Marwood or Gainford, still less of the castle, in Hugh Pudsey’s Domesday of Durham, the Boldon Book, compiled in 1133, for this is confined to the bishopric, within which the Baliol fee was not at that time included. Guy de Baliol received from William Rufus the Barony of Bywell, in Northumberland, and either from that king, or his father, the lordship of Gainford, of which he gave the church to St. Mary’s, at York. Bernard, his son and successor, was a distinguished adherent of Stephen, but lived into the reign of Henry II., and was one of those who broke up the siege of Alnwick, by the Scots, in 1174, before which time he probably built Barnard Castle. He also seems to have built the church, or rather chapel, of Barnard Castle town, and gave it also to St. Mary’s. He was succeeded by another Bernard, father of Hugh, father of John de Baliol, founder of Baliol College, Oxford, and of St. John’s Hospital, in Barnard Castle town, and regent of Scotland. He was born in the castle. He married Devorgoil, a co-heir of Alan, Lord of Galloway, from whom their son, another John, inherited the deadly claim to the throne of Scotland, which he made good, after a fashion, in 1292. He lost his English estates, and died at Château-Gaillard in 1314. Edward, his son, became king of Scotland, 1332, but was expelled in 1341, and died childless in 1363.