In this task, we ask you to elaborate the sentence without changing its general meaning. You can do so by explaining further the input sentence, using more precise wording, adding qualifiers and auxiliary information etc.

According to Frank Stenton " The continuous history of Northumbria , and indeed of England , begins with the reign of Athelfrith ... " Among the northern Angles , Aethelfrith was the first great leader .
The 20th-century historian Frank Stenton wrote that " the continuous history of Northumbria , and indeed of England , begins with the reign of Æthelfrith " , and that " he was the real founder of the historic Northumbrian kingdom , and he was remembered as the first great leader who had arisen among the northern Angles . "