 Up until about the time of his death , Diarmait had been the most powerful king in southern Ireland . In consequence of the void left by his demise , Diarmait 's <unk> ally Toirdelbach seized the initiative , and moved to enforce his own claim to the high @-@ kingship of Ireland . He immediately imposed his <unk> on Leinster — a task almost certainly expedited by the aforesaid infighting amongst the Uí Chennselaig — and took control of Dublin . Whilst the imposition of authority upon rival provincial kingdoms was a fundamental part in gaining the high @-@ kingship , Toirdelbach 's decision to march @-@ on Dublin reveals that the acquisition of this coastal kingdom had also become an essential part of the process . 
