St Columba in the context of "Derry"

The history of Christianity in Scotland includes all aspects of the Christianity in the region that is now Scotland from its introduction up to the present day. Christianity was first introduced to what is now southern Scotland during the Roman occupation of Britain, and is often said to have been spread by missionaries from Ireland in the fifth century and is much associated with St Ninian, St Kentigern (perhaps better known as St Mungo) and St Columba, though “they first appear in places where churches had already been established”. The Christianity that developed in Ireland and Scotland differed from that led by Rome, particularly over the method of calculating Easter, and the form of tonsure until the Celtic church accepted Roman practices in the mid-seventh century.

Christianity in Scotland is often said to have been strongly influenced by monasticism, with abbots being more significant than bishops, although both Kentigern and Ninian were bishops. “It is impossible now to generalise about the nature or structure of the early medieval church in Scotland”.In the Norman period, there was a series of reforms resulting in a clearer parochial structure based around local churches and large numbers of new monastic foundations, which followed continental forms of reformed monasticism, began to predominate. The Scottish church also established its independence from England, developing a clear diocesan structure and becoming a "special daughter of the see of Rome", but it continued to lack Scottish leadership in the form of Archbishops. In the late Middle Ages the crown was able to gain greater influence over senior appointments, and two archbishoprics had been established by the end of the fifteenth century. There was a decline in traditional monastic life, but the mendicant orders of friars grew, particularly in the expanding burghs. New saints and cults of devotion also proliferated. Despite problems over the number and quality of clergy after the Black Death in the fourteenth century, and evidence of heresy in the fifteenth century, the Church in Scotland remained stable.