<P> In 902 Máel Finnia mac Flannacain of Brega and Cerball mac Muirecáin of Leinster joined forces against Dublin, and "The heathens were driven from Ireland, i.e. from the fortress of Áth Cliath (Dublin)". They were allowed by the Saxons to settle in Wirral, England, but would however later return to retake Dublin . </P> <P> The Vikings never achieved total domination of Ireland, often fighting for and against various Irish kings . The Battle of Clontarf in 1014 began the decline of Viking power in Ireland but the towns which Vikings had founded continued to flourish, and trade became an important part of the Irish economy . </P> <P> By the 12th century, Ireland was divided politically into a shifting hierarchy of petty kingdoms and over-kingdoms. Power was exercised by the heads of a few regional dynasties vying against each other for supremacy over the whole island . One of these men, King Diarmait Mac Murchada of Leinster was forcibly exiled by the new High King, Ruaidri mac Tairrdelbach Ua Conchobair of the Western kingdom of Connacht . Fleeing to Aquitaine, Diarmait obtained permission from Henry II to recruit Norman knights to regain his kingdom . The first Norman knight landed in Ireland in 1167, followed by the main forces of Normans, Welsh and Flemings . Several counties were restored to the control of Diarmait, who named his son - in - law, the Norman Richard de Clare, known as Strongbow, heir to his kingdom . This troubled King Henry, who feared the establishment of a rival Norman state in Ireland . Accordingly, he resolved to establish his authority . In 1177 Prince John Lackland was made Lord of Ireland by his father Henry II of England at the Council of Oxford . </P> <P> With the authority of the papal bull Laudabiliter from Adrian IV, Henry landed with a large fleet at Waterford in 1171, becoming the first King of England to set foot on Irish soil . Henry awarded his Irish territories to his younger son John with the title Dominus Hiberniae ("Lord of Ireland"). When John unexpectedly succeeded his brother as King John of England, the "Lordship of Ireland" fell directly under the English Crown . </P>

When was ireland first invaded by the british