of the population of what is now Scotland practised a form of Celtic polytheism. Evidence of Christian symbols and the destruction of the shrines of other religions, suggest that Roman occupation brought Christianity to the north of Britannia (the name they gave to the province under their control in the southern part of the island). From there it may have spread to parts of what they called Caledonia (roughly corresponding to what is now Scotland). After the collapse of Roman authority in the early fifth century, four major circles of influence emerged in Northern Britain. In the east were the Picts, whose kingdoms eventually stretched from the river Forth to Shetland. In the west were the Gaelic (Goidelic)-speaking people of Dál Riata, who had close links with Ireland, from where they brought with them the name Scots. In the south were the British (Brythonic-speaking) descendants of the peoples of the Roman-influenced kingdoms of "The Old North", the most powerful and longest surviving of which was the Kingdom of Strathclyde. Finally, there were the English or "Angles", Germanic invaders who had overrun much of southern Britain and held the Kingdom of Bernicia (later the northern part of Northumbria), which reached into what are now the Borders of Scotland in the south-east. While the Picts and Scots would have remained pagan, most scholars presume that Christianity would have survived after the departure of the Romans among the Brythonic enclaves, but retreated as the pagan Anglo-Saxons advanced. The Christianisation of Scotland was carried out by Irish-Scots missionaries and to a lesser extent those from Rome and England. Richard Fletcher argued that motivations may have included the example of St. Patrick, the idea of Peregrinatio and a growing interest in evangelism. In the sixth century missionaries from Ireland were operating on the British mainland. This movement is traditionally associated with the figures of St Ninian, St Kentigern and St Columba. Ninian is now regarded as a later construct and may have been the result of scribal confusion with the Irish saint Finnian. There was a church dedicated to him at Whithorn in the sixth century and from there St Kentigern seems to have created a new centre of worship at Govan or Inchinnan, from where Christian influence extended across the Strathclyde region. St Columba was probably a disciple of Finnian. He left Ireland after being exiled, and founded the monastery at Iona off the