his demise could well have paved the way for Echmarcach's own rise to power. Having come to terms with the three kings, it is possible that Knútr relied upon Echmarcach to counter the ambitions of the Orcadians, who could have attempted to seize upon Hákon's fall and renew their influence in the Isles. Uí Briain alliance and the conquest of Dublin Following his meeting with Knútr, Echmarcach appears to have allied himself with the Uí Briain, the descendants of Brian Bóruma mac Cennétig, High King of Ireland. In 1032, the eleventh- to fourteenth-century Annals of Inisfallen states that Donnchad mac Briain, King of Munster married the daughter of a certain Ragnall, adding: "hence the saying: 'the spring of Ragnall's daughter'". This woman is elsewhere identified as Cacht ingen Ragnaill. Like Echmarcach himself, Cacht's patronym could be evidence that she was a near relation of the Ragnalls who ruled Waterford, or else a descendant of Ragnall mac Gofraid. She could have therefore been a sister or niece of Echmarcach himself. At about the time of his union with Cacht, Donnchad aspired to become High King of Ireland. With powerful maritime forces at his command, Echmarcach would have certainly been regarded as an important potential ally. Clear evidence of an alliance between Echmarcach and the Uí Briain exists in the record of a marriage between Echmarcach's daughter, Mór, and Toirdelbach Ua Briain's son, Tadc, preserved by the twelfth-century Banshenchas, a text which records the marriage of Echmarcach's daughter, Mór, to Tadc, son of Toirdelbach Ua Briain. Annalistic evidence of such an alliance is found well into the late eleventh century. In fact, kinship between Echmarcach's descendants and the Uí Briain even led to the accession of one of Echmarcach's maternal grandsons, Domnall mac Taidc, to the kingship of the Isles at about the turn of the twelfth century. If Echmarcach was a son of Ragnall mac Gofraid, this alliance with the Uí Briain would have been a continuation of amiable relations between the two families. For example, the father of Ragnall mac Gofraid appears to have combined forces with Brian Bóruma in 984, and Ragnall mac Gofraid himself is recorded to have died in Munster, the heartland of the Uí Briain. If, on the other hand, Echmarcach and Cacht were descended from the Waterford dynasty, an alliance between the Uí Briain and this family may have been undertaken in the context of