Kingship Under Pressure
The most consequential political development was the rise of Tairdelbach Ua Briain. A grandson of Brian Bóruma, he was the son of Tadc, who had been killed in 1023 at the instigation of Brian’s ruling son, Donnchad. Tairdelbach consequently had both a dynastic claim and a powerful personal reason to oppose his uncle. His chief patron was Diarmait mac Maíl na mBó, king of Leinster and ruler of Dublin, who was also his foster-father.