 The conflict between the Welsh princes and the English kings continued in the reign of Edward I. In 1282 Llywelyn fought a final campaign against Edward , ending in the prince 's death near Builth that December . His brother , Dafydd ap Gruffydd , assumed power but during 1283 was forced south into Snowdonia and by May his government was based from Dolbadarn Castle . Edward deployed 7 @,@ 000 troops to detain Dafydd who was finally captured and executed in October ; Dolbadarn was occupied by Norman forces . 
