Share, children. Share. History rewrites by the chroniclers serving the agenda of the king best equipped to chronicle, rule the day, but eventually some do get corrected.
Here, the chroniclers of Alfred the Great, King Alfred of Wessex, who beat back the Vikings at Edington and is therefore a great hero, had help. Not only help, but perhaps the efforts of the unsung King Ceowulf II, king of Mercia 874-877 were dispositive. Coins have been found that display Alfred and Ceowulf equally on the face of the coins. A few of them had been found earlier, but a new discovery shows the widespread dissemination of them and points to a strong alliance between the kings. See support at http://www.historyfiles.co.uk/FeaturesBritain/EnglandCeolwulf01.htm
Ceowulf is not only written out of history, the few accounts of him are unfavorable. See http://www.archaeology.org/issues/208-1603/trenches/4165-trenches-england-viking-hoard
Ceowulf was dismissed as a "foolish king's thane" holding lands for the interest of the Vikings in the Anglo-Saxon Chronicle, see historyfiles site, and http://www.anglo-saxons.net/hwaet/?do=get&type=person&id=CeolwulfIIofMercia, for example. Instead, he was independent, a "shrewd negotiator" (see anglo-saxons.net site), legitimate king, and with friendly relations as to Alfred.