Ua Brolcháin, Flaithbertach (d. 1175), abbot of Derry and comarba (coarb or successor) of Colum Cille, 1150–75, and noted church reformer, was apparently the son of Máel-Coluim Ua Brolcháin (d. 1122), bishop of Ardstraw in Cenél nÉogain. We first hear of him as the comarba of Colum Cille (qv) in 1150, with his seat at Derry, the chief house of the familia s. Columbae, when he made a formal visitation of the Columban houses in Cenél nÉogain. Further visitations of other parts of his ecclesiastical jurisdiction were made in 1151 and 1153. It is most probable that he attended the synod of Kells–Mellifont (1152). The synod of Brí meic Thaidc in Meath in 1158 recognised his status as chief abbot of the Columban confederation. In 1161 he attended the synod of Dervor, on the Meath–Cavan border, at which he reclaimed the ‘tributes and jurisdictions’ of ‘the churches of Colum Cille in Meath and Leinster’ (Annals of Ulster). Earlier that year, he made a circuit of Osraige during which he received payments of tribute.
In the course of his stewardship, with the support of Muirchertach Mac Lochlainn (qv), king of Cenél nÉogain and high-king of Ireland, Flaithbertach considerably developed and extended the physical fabric of the ecclesiastical buildings at Derry. In 1155 he had a new doorway constructed for the church and in 1164 he completed the great stone church. The Annals of Ulster relate that a delegation came to Derry that year to ask him to accept the abbacy of the Iona community, ‘but the coarb of Patrick [Gilla Meic Liac (qv), archbishop of Armagh] and Ua [i.e. Muirchertach Mac] Lochlainn, king of Ireland, and the nobles of Cenél nÉoghain prevented him’. Church rivalry may have been behind the burning of the churches and monasteries of Armagh and Derry in 1166.
Flaithbertach's death is recorded for 1175 in the Annals of Ulster where he is fulsomely described as a ‘tower of wisdom and hospitality, a man to whom the clergy of Ireland gave the chair of a bishop because of his wisdom and his excellence, and to whom was offered the succession of Iona’. Clearly he was one of the most important northern ecclesiastics of the later twelfth century.