William had inherited the title of Earl of Northumbria in 1152. However, he had to give up this title to King Henry II of England in 1157. He spent much of his reign trying to regain his lost territory. In 1173, whilst Henry II was occupied in fighting against his sons in the Revolt of 1173–1174, William saw his opportunity and invaded Northumbria. He advanced on Newcastle but found the partly built stone castle too strong to allow him to take the town. He also attacked Prudhoe Castle but found the defences too strong. Unwilling to undertake a lengthy siege, William returned to Scotland.