 The Normans conquest of England at first had little effect on North Wales . This was to change as the city of Chester on the River Dee became the base for successive campaigns against the country in the thirteenth century . The coastal plain of Clwyd was the main invasion route used and a number of castles were built there to facilitate these advances . The castles at Flint and Rhuddlan date from this period , and were the first to be built by Edward I of England in North Wales during his successful conquest in 1282 . After this , the rule of the Welsh Princes was at an end and Wales became annexed to England . The country was known as the Principality of Wales during the period 1216 to 1536 . From 1301 , the crown 's lands in north and west Wales , including Clwyd , formed part of the appanage of England 's heir apparent , who was given the title " Prince of Wales " . This was a time of repression for the Welsh people and there were numerous uprisings and rebellions against English rule . Under the Act of Union of 1535 , Wales became permanently incorporated under the English Crown and subject to English law . 
