"Glastonbury was the most ancient and venerable sanctuary of Our Lady in England. In 530 St. David of Menevia, accompanied by seven of his suffragan bishops, came to Glastonbury, invited thither by the sanctity of the place, and consecrated a Chapel of Our Lady on the east side of the church. As a mark of his devotion to the Queen of Heaven, he adorned the golden superaltar with a sapphire of inestimable value, known as the Great Sapphire of Glastonbury. The Silver Chapel of Our Lady was stored with costly gifts, the value of which, at our present standard, mounted to a prodigious sum. Among the Saxon kings who came hither on pilgrimage may be mentioned Athelstan and Edgar the Peaceable, the latter laying his sceptre on the Blessed Virgin's altar and solemnly placing his kingdom under her patronage." - The Catholic Encyclopedia.
Note: The uncle of St. David of Wales was one Melchinus, called Maelgwyn who wrote of St. Joseph of Arimathea at Glastonbury, and much more. As the Cornish Archaeologist Charles Thomas pointed out, there has been a direct unbroken continuity of Christian tradition in the 'cradle' of West England, South Wales, and Devonia since the first centuries of Roman-Britain til the present day.