Edmund II "Ironsides"
Towards the end of Æthelred's reign, one Eadric Streona appeared on the scene, and he and Æthelred quickly became as thick as thieves. The other people surrounding the king looked askance at Eadric, and not only because he was an upstart. The chronicle record various murders committed by Eadric; five in all, four on the same day. His preferred method seems to have been to invite his victim(s) to dinner and then kill him, an interesting twist on the laws of hospitality. On one occasion, Eadric had two men as guests, each of whom was accompanied by a manservant. Near the end of the meal, Eadric gave the signal and his men promptly killed the two guests. The servants of the murdered men tried to defend their masters, but only succeeded in getting themselves added to the list of People To Kill Today. They fled, on foot, and Eadric ordered his men not to pursue them. It would be much more efficient to go to the stables, saddle up some horses, and then pursue the two servants. This was done, but Eadric's calculations were off and they caught up with their prey only to find that the servants had taken sanctuary in a wooden church. Eadric ordered it burned to the ground. That done, Eadric got hold of the daughter of one of the murdered men and shipped her off to one of the royal residences, there to await Æthelred.
Now Æthelred's son Edmund happened to be living at that particular residence at the time, and he shortly wed the girl. Edmund already was strongly of the opinion that his father did not rule well. Knowing of Æthelred's possible complicity in and certain tolerance of the murder of his wife's father wouldn't have helped, nor would knowing the reason for his wife's sudden appearance on the scene. For whatever exact mix of reasons, Edmund declared civil war. This did not have time to get very far before there was another wave of Danish invasions, and a truce was called. It was agreed that Æthelred would be in of one army, and Edmund and Eadric jointly of another.
At the Battle of Scearstan, Edmund fought his way over to Cnute, and while the two of them were fighting, Eadric seized the opportunity to lop off the head of a man similar in looks to Edmund and hold it up for all to see, shouting that this was Edmund's head. The confidence of the Saxon army quickly evaporated, and most fled.
Later Eadric asked Edmund's forgiveness, and Edmund granted it, possibly becuase Eadric was his brother-in-law. Edmund fought more battles, with the military skill that earned him his nickname, and gained the upper hand. At the most inconvenient moment, Eadric again turned traitor, switching sides in mid-battle, along with the chunk of the army under Eadric's orders. Edmund retreated and went into hiding. When Cnute found him, Edmund had somehow gathered a new army, which, however, he offered not to use. He suggested single combat. Here chroniclers differ as to what happened. The interesting version is that Cnute agreed, they fought, and that when Cnute saw that Edmund was going to win, he proposed that they simply split the country. The less interesting version is that Cnute bypassed the fighting part--he was no fool--and suggested the split. In any case, the kingdom was divided between the two. Edmund got the south half and Cnute the north half, the half that was plagued by Scottish and Pictish raids. History does not record who decided who got which half.
A mere six months later, Edmund, in his early twenties still, was dead. The chronicles agree that he was murdered, but assign the blame to various quarters. Some accuse two chamberlains of Edmund, acting under the orders of Eadric Streona. Others accuse Eadric, acting under the orders of Cnute, the one with the motive. The most intiguing version is that Eadric murdered Edmund, or had him murdered, for Cnute, but without Cnute's knowledge. According to this version, Cnute only found out some time later, when he and Eadric were playing chess. Eadric was winning, Cnute wasn't happy and demanded that the rules be temporarily suspended. Eadric refused, and an argument ensued, during which the two took turns dredging up every past grudge and grievance they could think of. At last Eadric sneered that he had done everything for Cnute, selflessly, even down to murdering Edmund. Cnute was stunned and replied that Eadric had acted contrary to Cnute's own will, not to mention God's, and sentenced Eadric to death. It is a fact that Eadric was executed at about this time, but warring against the credibility of this story is an almost identical one; supposedly during another chess game, this time with Ulf Jarl, another heated argument ensued, this time resulting in Ulf throwing over the chess table rather than retract his move, and storming out. Cnute followed him as far as the doorway and whispered to the guard, "Kill him." The two stories make an improbable parallel, but on the other hand, as stories, they aren't too original; fiction would probably be more decorative. Who knows?