Hugh appears to have at once commenced the conquest of North Wales. As Professor Lloyd remarks, Domesday Book shows us Deganwy as the most advanced Norman post on the North Welsh coast, while on the Bristol Channel they had got no further than Caerleon.[837] In advancing to the valley of the Clwyd and building a castle at Rhuddlan, the Normans were only securing the district which had already been conquered by Harold in 1063, when he burnt the hall of King Griffith at Rhuddlan. Nearly the whole of Flintshire (its manors are enumerated by Domesday Book under Cheshire) was held by Earl Hugh in 1086, so that he commanded the entire road from Chester to Rhuddlan. His powerful vassal, Robert of Rhuddlan, who became the terror of North Wales, besides the lands which he held of Earl Hugh, held also directly of the King Rhos and Rhufeniog, districts which roughly correspond to the modern shire of Denbigh, and "Nort Wales" which Professor Lloyd takes to mean the remainder of the principality of Gwynedd, from which the rightful ruler, Griffith ap Cynan, had been driven as an exile to Ireland. It does not appear that there was any fortification at RHUDDLAN[838] before the "castle newly erected" by Earl Hugh and his vassal Robert. They shared between them the castle and the _new borough_ which was built near it.[839] One word about this new borough, which will apply to the other boroughs planted by Norman castles. There were no towns in Wales of any importance before the Norman Conquest, and this civilising institution of the borough is the one great set-off to the cruelty and unrighteousness of the conquest. Mills, markets, and trade arose where castles were seated, and civilisation followed in their train. The castle of Hugh and Robert was not the magnificent building which still stands at Rhuddlan, for that is entirely the work of Edward I., and there is documentary evidence that Edward made a purchase of new land for the site of his castle.[840] More probably Robert and Hugh had a wooden castle on the now reduced motte which may be seen to the south of Edward's castle. In Gough's time this motte was still "surrounded with a very deep ditch, including the abbey." Nothing can be seen of this ditch now, except on the south side of the motte, where a deep ravine runs up from the river. As from Gough's description the hillock (called Tut Hill)[841] was within the precincts of the priory of Black Friars, founded in the 13th century, it is extremely probable that Edward gave the site of the old castle to the Dominicans when he built his new one.[842]