"Æthelred was king of Northumbria in the middle of the ninth century, but his dates are uncertain. N. J. Higham gives 840 to 848, when he was killed, with an interruption in 844 when Rædwulf usurped the throne, but was killed the same year fighting against the Vikings. Barbara Yorke agrees, and adds that Æthelred was the son of his predecessor, Eanred, but dates his death 848 or 849. D. P. Kirby thinks that an accession date of 844 is more likely, but notes that a coin of Eanred dated stylistically no earlier than 850 may require a more radical revision of dates. David Rollason accepts the coin evidence, and dates Æthelred´s reign from c.854 to c. 862, with Rædwulf´s usurpation in 858." - (en.wikipedia.org 06.10.2020)
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