England–Wales border after Harold's death at the Battle of Hastings, Wales was again divided without a leader to resist the Normans. Immediately after the Norman conquest of England, King William installed one of his most trusted confidants, William FitzOsbern, as Earl of Hereford. By 1071 he had started the building of Chepstow Castle, the first castle in Britain built of stone, near the mouth of the Wye. It served as a base from which the Normans continued to expand westward into south Wales, establishing a castle at Caerleon and extinguishing the Welsh kingdom of Gwent. William also installed Roger de Montgomerie at
River Dee, Wales a mixed fishery with salmon and trout fishing, mostly in the upper waters and a good coarse fishery in the lower reaches. A major pollution incident in the middle reaches in the late 1990s did extensive damage to the fishery from which it is now largely recovered. River Dee, Wales The River Dee (, ) is a river in the United Kingdom. It flows through parts of both Wales and England, forming part of the border between the two countries. The river rises in Snowdonia, Wales, flows east via Chester, England, and discharges to the sea in an estuary between