Patrick is the apostle of Ireland, and unusually among early saints he left writings in his own hand, the Confessio and the Letter to Coroticus, which let us glimpse the man beneath the legend. He was not Irish but a Romano-Briton, carried off to Ireland as a slave in his teens, who escaped, returned home, entered the Church, and then went back to the land of his captivity as a missionary bishop in the fifth century. His own writings are spiritual and defensive rather than biographical, but they attest to a real and difficult mission among a non-Christian people. The famous legends, driving the snakes from Ireland, using the three-leaved shamrock to explain the Trinity, are later medieval accretions, not found in his own words; Ireland had no snakes to drive out, and the shamrock story appears only centuries later.
What is historical is his role in the Christianization of Ireland, which he helped set in motion and which, within a few generations, made the island a centre of monastic learning that would help re-evangelize parts of Europe. His feast on 17 March has become, far beyond its religious origin, the global celebration of Irish identity.