In the twelfth-century Cogadh Gáedhel re Gallaibh Brian’s second wife Gormlaith, daughter of the king of Leinster, is given a colourful role in the fatal march towards Clontarf and her husband’s murder. Geoffrey Keating picked up this theme in Foras Feasa ar Éirinn, where Gormlaith is pictured as rebuking her brother Máelmórda, who had inherited the Leinster kingship from their father, for accepting his position as subordinate chief to Brian. Máelmórda had acceded to Brian’s request that he bring to his palace of Kincora three large timber masts and in doing so he had torn the clasp on a tunic that Brian had given to him. When he asked his sister to mend the tunic, she thrust it angrily into the fire as a shameful badge of his slavery. Stung by her words, Máelmórda got drawn into a dispute with Brian’s eldest son Murrough over a game of chess, stormed out of the palace and began to plot the overthrow of Brian with the help of the Vikings. The story of Gormlaith’s fatal intervention was repeated by Hugh MacCurtin in 1717 but not by Sylvester O’Halloran in his influential account of the Battle of Clontarf. Popular histories in the nineteenth century also eschewed the more elaborate storyline, preferring an all-male narrative.
The one exception was M.F. Cusack (a.k.a. the Nun of Kenmare), whose Illustrated history of Ireland went through two editions in 1868 and who gave due emphasis to the role of Gormlaith, not alone in provoking her brother’s rebellion but also in aiding her son (by a previous marriage), the Viking chief Sitric of Dublin, in appealing for help from other Viking leaders in the Isle of Man and elsewhere. It is tempting to explain Cusack’s placement of a powerful woman in the foreground of her history in terms of her own position as a maverick and controversial figure in the nineteenth-century Irish Catholic Church. It may, however, owe more to the intensive research that she carried out, which drew not only on the newly translated Annals of the Four Masters (1848–51) but also on Icelandic saga accounts of Clontarf. Cusack’s depiction of the thrice-married Gormlaith as ‘remarkable for her beauty’ but also ‘proud and vindictive’ reflected the thrust of these sources, which invented the evil ways of Brian’s wife to counterpoint his qualities as a Christian king of piety and honour as well as of glorious military feats.