St. Joseph of Arimathea, acclaimed by the monastery of Glastonbury as the apostolic evangelist of Britain, gained this accolade through the Arthurian Grail romances, and most particularly, the Estoire del Saint Graal. Heretofore, the majority of those favoring the Christian origin of the Grail legend have plumbed the Bible, the apocrypha, and the Christian exegetical tradition in search of source elements of the Grail's history. Their research has been concentrated on the mystery of the Grail itself, or the pre-Britain adventures of Joseph and his followers. Some others have investigated various aspects of Celtic Christianity, particularly the assimilation of Celtic legends and narrative materials regarding Bran, son of Llŷr, into Christian tradition, as the genesis of Joseph's activities in Britain. This euhemerization of pagan folklore was a natural consequence of the pattern of Christianization established during the apostolic era, which attempted to build the new religion on the foundations of the old, retaining and adapting heathen practices which were consonant with Christianity. A few, notably Roger Loomis, studied the impact of these euhemerized legends on the Grail history, pursuing the mutations of the myths through oral transmission, in accordance with the process outlined by the noted Bollandist, Père Hippolyte Delehaye. Still others correlated the religious elements of the entire Joseph/Grail saga with the history and characteristics of the Celtic Church in Wales, with strong overtones of heterodoxy.