Leinster was probably the province in which Christianity was already most strongly represented, and Patrick may have entrusted this part of his sphere to two fellow-workers from Gaul, Auxilius and Iserninus.
The Brehon Laws assume the existence of married as well as unmarried clergy, and when St Patrick was seeking a bishop for the men of Leinster he asked for " a man of one wife."
In 590 Columbanus, a native of Leinster (b.
Aed lost his life in endeavouring to exact the boroma tribute from Brandub, king of Leinster, who defeated him at Dunbolg in 598.
As a sequel Fergal's son, Aed Allan (734-743), defeated the men of Leinster with great slaughter at Ballyshannon (Co.