 Bede , paraphrasing Virgil , wrote that following Ecgfrith 's death , " the hopes and strengths of the English realm began ' to waver and slip backward ever lower ' " . The Northumbrians never regained the dominance of central Britain lost in 679 , or of northern Britain lost in 685 . Nonetheless , Northumbria remained one of the most powerful states of Britain and Ireland well into the Viking Age . 
