Sigeberht found a powerful northern "friend" ("amicus") and ally in King Oswiu of Bernicia (r. 642–670). Bede's statement that Sigeberht regularly visited the Bernician court and the general nature of Oswiu's influence on the course of Sigeberht's career suggest that the balance of power was in Oswiu's favour. Oswiu may have intended the alliance to help him offer effective resistance against King Penda of Mercia, as is also suggested by his alliance with Penda's son Peada, king of the Middle Angles.