Being a ruler in the Dark Ages was fraught and forever overshadowed by the ever-shifting clouds of uncertainty. The short reign of Ethelfrith came to a bloody climax in 616 when Redwald killed him somewhere near the east bank of the River Idle at Hatfield Chase near Doncaster. Edwin succeeded him as king of Northumbria, and the next year led his Northumbrian army against Elmet. This well-planned offensive succeeded in overthrowing Ceretic, the last surviving British king. Just a few miles east of Leeds, near Aberford, some impressive linear earthworks may have had strategic importance for Ceretic in his defence of Elmet from attack by the English. From the direction the rampart faces, this would appear to be possible at South Dyke, a mile east of Green Hill. However, in the case of a second site, the larger, more impressive dimensions suggest it might have been a frontier defence thrown up by the Northumbrians against Mercian aggression from the south. From a point about half a mile east of Potterton Bridge near Barwick in Elmet, this massive earthwork stretches east for two miles. Marked on maps as The Ridge and Becca Banks, it runs almost parallel to the north bank of Cock Beck as far as Aberford. It continuation, The Rein, can be picked up again just beyond the A1 from where it trends south-east for a mile and a half in a straight line, ending near Lotherton Hall beside the B1217.
Other earthworks in the Elmet area that may also be late-6th century include the hill fort at Barwick in Elmet and another series of trenches in Huddleston Old Wood, between Mickelfield and Sherburn in Elmet. From the extent of these earthworks as a major offensive must have been expected, but from which quarter is not certain. Standing upon these ramparts in the very heart of Elmet evokes the gruesome aftermath of the heavy hand-to-hand combat that must have taken place around these frontier works. The defeat of the British at Elmet and subsequent toppling of their heathen icons signalled the emergence of English Christianity during the early 7th century. In 619 king Edwin married Ethelburga, a Christian princess from Kent, and a year later was himself converted to the faith at Goodmanham in the East Riding. That same year one of Edwin's ministers, Lilla, was killed in a heroic sacrifice bear the river Derwent, when he threw himself upon an assassin's blade to protect Edwin. According to tradition Lilla was later buried within a large Bronze Age round barrow on the North York Moors. This is located on Fylingdales Moor within sight of the M.O.D. early warning station. When excavated, the mound revealed jewellery and ornaments of gold and silver.