The Political Climate of 1460-61: When Edward IV assumed the throne in 1461, he became the third king to depose a living monarch since the Norman Conquest in 1066. Like his predecessors, he faced the difficult task of reuniting a divided country. But unlike his predecessors, he had to cope with not only a living ex-king but a whole ex-dynasty at liberty and commanding the loyalty of a significant political faction.
The deposition of Henry VI differed from those of Edward II and Richard II in several important respects. Edward II resigned his crown in 1327, ostensibly of his own free will, in favor of his son Edward III and died shortly thereafter at the hands of his captors. Some seventy years later, the childless Richard II also signed away his rights of kingship to Henry IV, and likewise died a few months later.
Edward IV had no convenient legal fiction of the blessing of an abdicating king to strengthen his claim, nor did he have Henry VI in his custody. Instead, Henry VI enjoyed both liberty and relative safety across the border in Scotland, along with his assertive wife and young son and a number of influential nobles who remained loyal to his cause. Both Scotland and France saw an opportunity to weaken their English opponents by encouraging a continuation of civil war, and Edward found himself facing both an actual Scottish invasion and a rumored French one on the eve of his coronation.
With Henry's adherents potentially able to muster so much domestic and foreign support, it was thus vital for Edward to solidify his base of Yorkist supporters, to win over as many neutral nobles and gentry and members of the opposition as possible, and to demonstrate to England's neighbors that the Yorkists had a firm grip on the machinery of government and the support of both the magnates and the people. Without the acquiescence of Henry VI in his own deposition, Edward had an urgent and pressing need to validate his claim to the throne by right of heredity, by conquest, and by divine approval.
Edward's coronation, which he could expect all but his most vehement opponents to attend, was the perfect occasion to state his case to a wide audience by all the means at his disposal. If he could win the support of those who attended his coronation, he could count on them in turn to influence their own supporters when they returned to their homes. To do so, Edward IV and his supporters used every persuasive technique at their command, including the propaganda genealogy.