The Story of Norway by Hjalmar Hjorth Boysen

The legitimate heir to the throne after Haakon's death was his nephew, Guttorm Sigurdsson, a son of his brother, Sigurd Lavard. In spite of his tender age, the Birchlegs made haste to elect him, with the understanding that Haakon Galen, with the title of earl, should conduct the government. There were, however, some of the Birchlegs who were dissatisfied with this arrangement, partly because they were jealous of Haakon Galen, partly because they felt that, in such troublous times, a king was needed, who should be something more than a name or a figure-head. The Baglers, too, strange to say, were ill at ease, because they feared that, Haakon Sverresson's restraining influence being removed, the Birchleg chiefs would give free rein to their passions of avarice and vengeance. Half in self-defence they, therefore, reorganized their troop under the leadership of an impostor, calling himself Erling Stonewall (Steinvegg), who pretended to be a son of King Magnus Erlingsson.

A pretender of this name had, during the reign of Sverre, made some little stir, and had been imprisoned by King Knut of Sweden in a tower, whence he had escaped by means of a rope, made out of his bed-clothes. The rope proved, however, to be too short, and in letting himself drop to the ground, Erling broke his hip. He was overtaken, on his flight, by Sverre's men and in all probability slain. Nevertheless, it required audacity rather than proof of royal birth, in those days, to figure as a pretender; and the second Erling Stonewall, though probably few at first believed in him, soon had a considerable following. It was of no use that Bishop Nicholas opposed him, and urged his own nephew, Philip, a grandson of Harold Gille's queen, Ingerid, for the chieftainship.