Rainer Wälde

Describes some of the missionary activities of Saint Columbanus and Saint Gallus of the ancient Celtic Church. (The unique flavor of Celtic Christianity was largely lost after the Celtic Church's adoption of Latin at the behest of the Latin Pope and the consequent "regularization" of the Celtic Church by the Latin Church in the 8th century.)

A good overview of what remains of our knowledge of ancient Celtic Christianity, which was largely lost after the Celtic Church's adoption of Latin at the behest of the Latin Pope and the consequent "regularization" of the Celtic Church by the Latin Church.