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 13th century. The coastal plain of Clwyd was the main invasion route, and a number of castles were built there to assist 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 was annexed to England. This area was known as the Principality of Wales from 1216 to 1536. From 1301, the Crown's lands in north and west Wales formed part of the appanage of England's heir apparent, who was given the title "Prince of Wales". Under the Laws in Wales Act of 1535, Wales became permanently incorporated under the English Crown and subject to English law.