Ireland took place by an English king - Ecgfrid of Northumbria - who used the need to enforce conformity of religious practice on the Irish as a pretext for his military expedition. Thereafter, to Roman practices. This took centuries to effect with further military and political pressures being brought to bear.

THE NORMANS

During the era of the Celtic Church, Ireland continued to be divided into many Celtic kingdoms (Irish - tuatha) each with its own king (Irish - ri). Some of these kings were overlords with the five provinces of Ulster, Connaught, Munster, Leinster and Meath (Tara) each having a king. The idea of the high king (Irish - ard-ri) of Ireland was more of an aspiration than a reality with only a few outstanding figures such as Brian Boru, the hero who defeated the Vikings at Clontarf in 1014AD, maintaining a tenuous hold on the position for a few years. In this period the Irish Church retained some of its distinctive features but as it became increasingly embroiled in the politics of the various rival kings its moral authority and spiritual vitality lapsed. The shock of the Viking invasions subsided and the Norsemen began to intermarry with the Celts, being assimilated into Irish society as the ‘Ostmen’ - men of the Eastern seaboard.

They were the first to recognise the jurisdiction of Canterbury over the island of Ireland and archbishops of Armagh and Dublin were, for a time consecrated by the Archbishop of Canterbury. Only after a period of internal ecclesiastical* reform under Malachy in the twelfth century did the Ostmen return their allegiance to the Irish Church. The Synod of Kells in 1152 re-organised the Church into Roman style dioceses with four archdioceses at Armagh, Dublin, Tuam and Cashel. Consequently, the Irish Church, regained its independence from Canterbury, and Armagh was recognised as the undisputed ecclesiastical capital of Ireland. In these political and ecclesiastical manoeuvres the seeds of the Norman invasion were sown.

For some time Ireland had been moving slowly towards accepting a strong central monarchy but no properly defined system of selection had emerged. Rival Gaelic kings vied for the honour, some managing to exert a degree of real control over the other kings, others becoming high king in name only. During one of the many episodes of wrangling over the high-kingship with churchmen as well as soldiers taking sides, Dermott Mac Murrough, king of Leinster was attacked by an ally of the high king Rory O'Connor in 1166. Dermott fled to England to look for support. He landed in Bristol where he was advised to seek out Henry II, the Norman king who was then resident in Aquitaine in France. Henry gave Dermott permission to recruit among his subjects and Dermott’s quest brought him to an Anglo Norman warrior known as Strongbow: Richard FitzGilbert de Clare, the Earl of Pembroke who was engaged in an ongoing war with the native Welsh. In return for Dermott’s daughter Aoife’s hand in marriage and the right to succeed him as king of Leinster, Strongbow agreed to assist Dermott.

The Normans were disciplined and ruthless warriors and after moderate success under Dermott's banner they defeated both the Ostmen and the native Irish under Strongbow’s command in 1170. Strongbow married Aoife and having routed Rory O’Connor and his armies, was in a strong position to dominate the entire island. This possibility threatened Henry who decided that he needed to extend his kingship over Ireland as well as England rather than face the prospect of a rival Norman kingdom in Ireland.

Once again, the marriage of Church and State played a pivotal role in the story that was about to unfold. The English Pope, Adrian, had issued a bull in 1155, recognising Henry as Lord of Ireland and commissioning him to carry out ecclesiastical reforms in the island. 

*ecclesias'tical - relating to the church or to the clergy.