Saint Ninian
In the letter Patrick announces that he has excommunicated Coroticus's men. The identification of Coroticus with Ceretic Guletic is based largely on an 8th-century gloss to Patrick's letter. It has been suggested that it was the sending of this letter which provoked the trial which Patrick mentions in the "Confession". The "Apostate Picts" are the Southern Picts converted by Saint Ninian and ministered to by Palladius, and who had subsequently left Christianity. The Northern Picts of Fortriu were later converted by Saint Columba in the 6th century, and as they were not yet Christian, they could not be called "apostate".