The Story of Norway by Hjalmar Hjorth Boysen

It was a dangerous precedent Sverre established when, without any other proof of his royal birth than his own assertion, he ascended the throne of Norway. The prospect was thus opened to any ambitious adventurer, skilled in mendacity and the use of arms, to snatch the crown at the point of the sword. The mere fact that a doubt existed in the minds of many, as to Sverre's origin, was in itself demoralizing. It destroyed that bond of loyalty which had hitherto bound the people to the descendants of Harold the Fairhaired, and made it easy for unscrupulous pretenders, by the prospect of booty, to entice men into rebellion. We see, therefore, during Sverre's reign and that of his immediate successors, an abundant crop of pretenders and rebellious bands start up in different parts of the country, only to be cut down after a more or less extended existence by the constituted authority.

That Sverre, in a measure, had himself to thank for this state of things he must have been well aware; and the frequency of his insistence upon his mission to deliver Norway from the illegal sway of Erling Skakke's son shows how anxious he was, lest the same thought should occur to others. Even though he was the son of Sigurd Mouth (which, is indeed, probable), he must have seen that the people were suffering no hardships from Magnus' mild exercise of his power, while the wars which were directly and indirectly inflicted upon the realm by his own pretendership shook it to its very core. In the role of a deliverer Sverre was therefore scarcely sincere, and a certain insecurity in his position, springing, perhaps, from an inward doubt, made him at times appear with less dignity than we might expect in a man of his genius and power.