Christianity probably reached Britain around 200 AD. Most likely brought to the island by Roman traders and settlers, many being persecuted by the Roman authorities. Over the centuries things changed, and The Edict of Milan gave religious toleration. By 378 AD, Christianity had become the State religion. The Church that had evolved in the islands was rooted in the monastic movement, and was to have profound impact upon the Celtic nations forming among the islands. It was to have its own special character and developed along its own teachings and customs. Through Brittany, Cornwall, Ireland, Scotland, and Wales, this Celtic Church took its roots. After the fall of Rome, this Church was isolated from the Church at Rome until St. Augustine arrived in 597 AD. However, it was not until 768 AD that the Celtic Church conformed to the supremacy of Rome.
The Celtic Church in Wales began its history among the tribal territories that occupied the landscape. Once a religious centre was established, it was a "Llan", meaning an enclosure that centered around a local church. This was of course "family land" and the name of the head of the family often followed this term. In "A Gazetteer of Welsh Place-Names", the spelling "Llan...." is the most common occurring place name starting with "Llanaber" on page 57, and ending with "Llan-y-wern" some 14 pages later!
It was often the case that family members would become the ministers of these family churches. They would become part of the family heritage, and would be past down from generation to generation. The drawing above locates the four major "modern dioceses" of the Church of Wales. They began in the mountains and moved into the "Llan...". These four major dioceses are listed from their mountains, to Celtic tribe, to Welsh Kingdom, to the principle religious center: 1) Snowdona - Decangi - Gwynedd - Bangor, 2) Berwyn - Ordovices - Powys - St. Asaph, 3) Plinlimmon - Demetae - Dyved - St. David's, and 4) Black Mountains - Silures - Morgannwy - Llandaff. One of the earliest centers called Bangor-Is-Coed is also shown which was located along the Dee. Mountains to ministers, the Celtic Church was formed.