The earliest event of Irish history that bears a well authenticated date is the mission of Palladius to Ireland in A.D. 431. The record of this year is found in the contemporary chronicle of Prosper of Aquitaine. In another work written a few years later. Prosper writes of the institution of a christian church in Ireland by Pope Celestine, who died in 432. All the early Irish sources agree in dating the mission of Patrick in 432.
Seven years later, the Annals of Ulster and the Annals of Inisfallen have the entry, derived from an earlier common source: ‘ Secundinus, Auxilius, et Iseminus mittuntur in Hiberniam in auxilium Patricii ’ A short tract copied in the Book of Armagh and dating probably, like the other documents in the same collection, from about 700, tells that Auxilius and Iserninus were sent by Germanus. It is silent regarding Secundinus.