St. David, also known as Dewi Sant,e Patron Saint of Wales and it is celebrated as a patriotic and cultural festival in Wales. St David was born in Cardiganshire and became renowned as a preacher and teacher. He founded many monastic settlements in Wales, Pembrokeshire and Brittany. It is claimed that St. David lived for over 100 years, and that he died on a Tuesday 1 March which is now celebrated as St. David’s Day. It is generally accepted this was around 589. He is also said to have founded Glastonbury Abbey.

Approximately forty years later William of Malmesbury, believing the Abbey older, decided that St. David had only rededicate the Abbey. William of Malmesbury is also said to have donated a travelling altar including a great sapphire. Apparently he had had a vision of Jesus telling him that Jesus himself had founded and dedicated the church in honour of His Mother. It was not seemly that it should be re-dedicated by human hands". So William decided that St David instead commissioned an extension to be built to the abbey, east of the Old Church. (Apparently the dimensions of this extension given by William were verified archaeologically in 1921).

Sapphire altar

There is a manuscript which indicates that a sapphire altar was among the items King Henry VIII confiscated from the abbey when it was sacked during the dissolution a thousand years later.