The name originally given to the Church in the British Isles before the mission of St. Augustine of Canterbury (d. 604) from Rome (596-97). It was founded by the second century, mainly among the poor, by missions from Rome and Gaul. By the fourth century, it was sufficiently established to send delegates to the Synod of Arles in 314 and the council of Ariminum in 359. All the evidence indicates that the Celtic Church was little affected by the major heresies of the age. It was in frequent contact with the Church of the Continent and immediately adopted the decisions of Pope Leo I in 455 about the date for Easter. It sent missions to Scotland, Wales, and Ireland. With the coming of Saxons in the fifth century, the Celtic Church was submerged along with the Celtic culture.