mission · 431 · Ireland
Prosper of Aquitaine — seed 182 — records under the year 431 that Palladius was ordained by Pope Celestine and sent as first bishop to the Irish believing in Christ. The last four words are the whole point. There were already Christians in Ireland in 431, enough of them to need a bishop, before Palladius arrived and before any date given for Patrick. Who they were and how they got there is not recorded; trade with Roman Britain and Gaul is the ordinary explanation, and Irish raiding, which brought Patrick himself over as a slave, is another. What happened to Palladius afterwards is unclear — later Irish tradition has him leaving quickly or dying in Britain, and some of the deeds attributed to Patrick may be his, since Armagh had every reason to consolidate two missionaries into one founder. This dataset keeps him separate for exactly that reason, and the profile says why: a founder legend absorbs its predecessors, and the way to resist that is to keep the predecessor on the page.
Was Patrick the first?
No, and the evidence is one sentence in a chronicle by a man on this dataset's own list.