To Hereford, on the Wye, William Fitz-Osbern came. He was the ablest, perhaps, of all the followers of the Conqueror. He entered Wales; he saw it from the Wye to the sea, and he thought it was not large enough, and that it was too far from the political life of the time. So he went back to Normandy, but he left his sons William and Roger behind him. William had his father’s wisdom. Roger had his father’s recklessness in action; he rebelled against his own king, and found himself in prison. The king sent him, on the day of Christ’s Passion, a robe of silk and rarest ermine. The caged baron made a roaring fire, and cast the robe into it. “By the light of God,” said William the Conqueror, for that was his wicked oath, “he shall never leave his prison.” But another Norman, Bernard of Neufmarché, came to take his place. He built his castle at Brecon, and defeated and killed Rees, the King of Deheubarth; and, with great energy, he took possession of the upper valleys of the Wye and the Usk. Further south William the Conqueror himself came to Cardiff, and possibly built a castle. The Norman conquest of the south coast of Wales was exceedingly rapid, and castle after castle rose to mark the new victorious advances—Coety, Cenfig, Neath, Kidwelly, Pembroke, Newport, Cilgeran. So far, the Norman advance has been a most quick one. In less than twenty-five years from the appearance of the Conqueror at Chester, the whole country had been overrun except the mountains of Gwynedd and the forests of the Deheubarth. This success is easily explained. For one thing, the Normans had trained, professional soldiers, who were well horsed and well armed. In a pitched battle the hastily collected Welsh levies, unused to regular battle and very lightly armed, had no chance. Again, the Norman never receded. He was willing to stop occasionally, in order to bide his time; but he clung tenaciously to every mile he had won. His skill as a castle builder was as striking as his prowess in battle or his cautious wisdom in council. He took possession of an old fortified post, or hastily constructed one of turf and timber; but he soon turned it into a castle of stone. At that time the Welsh had no knowledge of sieges; and their impetuous valour was of no use against the new castles.