After the Romans had left Britain (A.D. 410) the islands probably remained, like West Cornwall, independent of the Saxons; and when four centuries later the Northmen came to harry the country, they were joined by Welsh and Cornish Celts, glad of the chance of a blow at their common foe the Saxon. Scilly was then used by the Northmen as a sort of “naval base,” from which expeditions were made against the mainland. King Athelstan sent a fleet to oust them in 927, and left a garrison on the largest island; afterwards, in fulfilment of a vow, he founded a collegiate church at St. Buryan in Cornwall to commemorate his conquest. It is uncertain at what date the Benedictine monks first came to Scilly. Some say it was in 938. According to the Saga of King Olaf Tryggwason there was on Tresco in his time “a famous abbot, the head of a great cloister.” The story goes that the young Viking, in about the year 993, came harrying the coasts of England with a fleet of ninety-three ships, and was driven by contrary winds to the Isles of Scilly. Here he heard of a wonderful Christian hermit, who lived in a cell among the granite rocks and was said to possess the power of prophecy. Olaf was then in the position of a seeker after truth. He was inclined towards the religion of the Christians, but he had never acknowledged himself as one of their number. He was seized with curiosity to test the powers of the hermit, so he dressed up one of his tallest and handsomest followers in his own armour and bade him go to the cell and pretend he was the King. The disguise was quite useless. “You are no king,” said the hermit, “and I advise you to be faithful to your King.” On the strength of this proof, Olaf went himself to the cell to make inquiries concerning his own future. The hermit foretold that he should not only become a renowned king and perform many famous deeds, but that (far greater honour!) he should lead many into the true Christian faith. And for a sign he told him that on returning to his fleet he would meet with foes, a battle would be fought, he would be wounded severely and be carried on a shield to his ship, but would recover after seven nights and would soon after be baptized. Events happened just as had been predicted, and Olaf was so much impressed that as soon as he had recovered from his wound he put himself under the hermit’s instruction, and enrolled himself as a servant of the God of the Christians. Afterwards he went to Tresco, where was “a famous abbot, the head of a great cloister,” who with his brethren came down to the shore to meet the King and welcome him with all honour. They gave him further instruction in the Christian faith, and finally he and all his company were baptized. He appears to have spent several years in Scilly; and when he returned to Scandinavia, it was to devote his energies to preaching, in his native land and in Iceland, the Gospel which he had learnt to love in these remote islands.