remains of a previous fortification constructed by Maelgwn Gwynedd, a king of Gwynedd in the 6th century, although no such remains have been found. As part of his strategy for dealing with the Marcher Lords, Llywelyn married his eldest son, Dafydd, to Isabella, the daughter of William de Braose, a powerful lord in Brecon, Builth and Abergavenny. The Marcher Lords had adopted a style of stone castle that included circular keeps and an integrated system of curtain walls. Following Dafydd's marriage, Llywelyn appears to have started a second phase of building at Dolbadarn, probably in the 1240s, adding these elements to the existing castle. The prince was probably aiming not only to incorporate the latest military technology, but also to create a castle of equal prestige to those of his new allies in the south. Traditionally the surrounding district of Is Gwyrfai had been run from the town of Llanbeblig; after the 1240s, this role was transferred to Dolbadarn. 1240–1300 Following Llywelyn's death in 1240, Gwynedd's power declined and many of its eastern lands were taken by Henry III of England in 1247. Llywelyn's grandson, Llywelyn ap Gruffudd, took power in 1255 and imprisoned his brother Owain ap Gruffudd before extending his power across Wales. Owain was eventually released in 1277 and there has been much historical debate over which castle he was held in. Hywel Foel ap Griffri wrote a famous poem describing Owain's long imprisonment in a round tower; historians believe that this refers to the keep at Dolbardarn. 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. Edward was determined to prevent any further rebellion in North Wales and set about building a sequence of new castles and walled towns, replacing the old Welsh administrative system with a new principality governed from Caernarfon. Dolbadarn was no longer relevant and within two years timber from the castle was being used by the Normans for the construction of Caernarfon Castle. This was both a practical and a