Excerpts from Books and Wikipedia
"The western island of Ireland, never occupied by Roman soldiers or crisscrossed with Roman roads, was taking its own winding path towards nationhood. . . . In 451, the strongest tribe in Ireland was the Venii, or Feni, and the strongest clan of the Feni was the Connachta. The leader of the Connachta family was named Niall of the Nine Hostages, and his mother was Roman; . . . During one of these raids, he captured a Romanized Briton named Patricius and took him back to Ireland as a slave, where Patricius served for six years before stowing away on an Irish raiding ship and escaping into Gaul when it docked. There, he was converted to Christianity and had a vision calling him to return to the land of his slavery and teach the Irish of Christ. . . . While interfamily warfare went on around him, Patricius devoted himself to the spread of Christianity, so successfully that Ireland became Christian long before the British island to the east. . . . By the time of Patricius’s death, sometime before 493, three sons of Niall held power over three kingdoms in the northern half of the island . . . Their descendants would rule as the Ui Neill dynasty for six hundred years . . . " [Bauer: Medieval World, p. 125-8]