 Ecgfrith was killed during a campaign against his cousin , the King of the Picts Bridei map Beli , at a battle known as Nechtansmere to the Northumbrians , in Pictish territory north of the Firth of Forth . Bede recounts that Queen Eormenburh and Cuthbert were visiting Carlisle that day , and that Cuthbert had a premonition of the defeat . Ecgfrith 's death threatened to break the hold of the descendants of Æthelfrith on Northumbria , but the scholar Aldfrith became king and the thrones of Bernicia and Deira remained united . 
