St Rumon, also known as Ruan, Ronan, and Ruadan, was probably a brother of Bishop St. Tudwal of Trequier, but nothing else is known of him beyond that he was probably an Irish missionary and many churches in Devon and Cornwall in England were named after him. Rumon is a saint of some controversy. He is chiefly the patron of Tavistock in Devon, but also apparently of several churches in Cornwall and Brittany where he is variously called Ruan or Ronan.
Some authorities believed he is the same as the St Ronan (June 1) venerated in Brittany and believed consecrated bishop by St. Patrick, but others believe that he and St. Kea were British monks who founded a monastery at Street Somerset.
There was much quarreling over Rumon's holy body after his demise. His companion had thought to keep one of his arms as a relic and brutally cut it off. A disturbing dream soon made him put it back though. Later, the Princes of Cornouaille, Rennes, and Vannes all claimed the honor of burying him in their own province. The matter was decided by allowing him to be drawn on a wagon by two three-year-old oxen who had never been yoked. Where they rested, he would be interred. However, the body would not allow itself to be lifted onto the cart, except by the Prince of Cornouaille; so it was no surprise when the cattle chose Locronan in the Forest of Nevez, near his former home.
It is unclear when Rumon's relics left Locronan - despite the 16th-century shrine still to be seen there today. It was suggested by Baring-Gould & Fisher that they were removed to safety in Britain during the Viking coastal attacks of AD 913 & 14. Tradition says they were taken to Quimper, thence to Ruan Lanihorne in Cornwall. In AD 960, however, Earl Ordgar of Devon founded his great Abbey of Tavistock, on the edge of Dartmoor. He translated the body of Rumon into the abbey church with much pomp and ceremony and there it remained, working miracles for nearly six hundred years: until the Dissolution of the Monastery in the late 1530s. Some relics, however, may have made their way back to Brittany, by the 13th century, including, perhaps, his head.
Rumon's feast day is variously given as 1st June (in Brittany), 22nd July (in Ireland) and 30th August (in England); perhaps around AD 560.