563 Columba arrived in Dál Riata from his homeland of Ireland and was granted land on Iona. This became the centre of his evangelising mission to the Picts. When Æthelfrith of Northumbria was killed in battle against Edwin and Rædwald at the River Idle in 616, his sons fled into exile. Some of that time was spent in the kingdom of Dál Riata, where Oswald of Northumbria became Christian. At the death of Edwin's successors at the hand of Cadwallon ap Cadfan of Gwynedd, Oswald returned from exile and laid claim to the throne. He defeated the combined forces of Cadwallon and Penda of Mercia at the Battle of Heavenfield. In 634, Oswald, who had spent time in exile at Iona, asked abbot Ségéne mac Fiachnaí to send missioners to Northumbria. At first, a bishop named Cormán was sent, but he alienated many people by his harshness, and returned in failure to Iona reporting that the Northumbrians were too stubborn to be converted. Aidan criticised Cormán's methods and was soon sent as his replacement.<ref>[http://justus.anglican.org/resources/bio/52.html Kiefer, James E., "Aidan of Lindisfarne, Missionary", Biographical Sketches of memorable Christians of the past", Society of Archbishop Justus. 29 August 1999]</ref> Oswald gave Aidan the island of Lindisfarne, near the royal court at Bamburgh Castle. Since Oswald was fluent in both one of the and Irish, he often served as interpreter for Aidan. Aidan built churches, monasteries and schools throughout Northumbria. Lindisfarne became an important centre of Insular Christianity under Aidan, Cuthbert, Eadfrith and Eadberht. Cuthbert's tomb became a center for pilgrimage. Monastic foundations Around 630 Eanswith, daughter of Eadbald of Kent, founded Folkestone Priory. William of Malmesbury says Rædwald had a step-son, Sigeberht of East Anglia, who spent some time in exile in Gaul, where he became a Christian. After his step-brother Eorpwald was killed, Sigeberht returned and became ruler of the East Angles. Sigeberht's conversion may have been a factor in his achieving royal power, since at that time Edwin of Northumbria and Eadbald of Kent were Christian. Around 631, Felix of Burgundy arrived in Canterbury and Archbishop Honorius sent him to Sigeberht. Alban Butler says Sigeberht met Felix during his time in Gaul and was behind Felix's coming to Anglo-Saxon England. Felix established his episcopal see at Dommoc and a monastery at Soham Abbey. Although Felix's early training may have been influenced by the Irish tradition of Luxeuil Abbey, his loyalty to