Bernicia alone, though distracted by civil war between rival claimants for its throne, refused to yield.

Year by year the Mercian king carried his ravages over the north; once he reached even the royal city, the impregnable rock-fortress of Bamborough.
Despairing of success in an assault, he pulled down the cottages around, and piling their wood against its walls fired the mass in a fair wind that drove the flames on the town.

"See, Lord, what ill Penda is doing," cried Aidan from his hermit cell in the islet of Farne, as he saw the smoke drifting over the city, and a change of wind--so ran the legend of Northumbria's agony--drove back the flames on those who kindled them.

But burned and harried as it was, Bernicia still clung to the Cross.

Oswiu, a third son of AEthelfrith, held his ground stoutly against Penda's inroads till their cessation enabled him to build up again the old Northumbrian kingdom by a march upon Deira.