King Emrys III of Prydain, the last of the House of Dyfnaint, died childless in January 1078 without naming an heir. The most obvious candidate to succeed him was his brother-in-law, Gruffydd ap Culhwch, who came from one of the most powerful famlies in the realm. After gaining the support of other great nobles Gruffydd was crowned king on the royal hill of Ynys Wydryn on the 28th January.