Strong-muscled, healthy and with a lifetime of service before them, young men make the best slaves.
Snatched by Irish raiders to his home town on the Cumbrian coast, the preacher's boy learnt the strange Ulster dialect of his Celtic mother-tongue whilst looking after animals in the hills of what we call County Antrim. After a few years he escaped and did what we'd all do. He went home.
Later, with renewed Christian faith and a vision that the Irish needed to hear the great news about God, Jesus, forgiveness and new life, Patrick again set his eyes westward and cast off into the unsure.
To us, the details of Patrick's life are a mix of debated record and myth. But the result of his life is indisputed: the birth of faith in Jesus in the hearts of our forebears, a legacy for countless generations whose importance transcends ethnicity, politics and our ideas on theology.
As we raise our glasses of Guinness today to a chorus of "cheers" or "sláinte", let us pause and reflect - as the cool pride of Ireland guilds our throats - how much courage must it have taken to leave, this time willingly, and return across the Irish Sea.
Given the dangers, Patrick must have been a man transformed, on fire with conviction! May that passion for Christ grip us all.