There seems to be some dispute over who founded a monastery at Drumlane, County Cavan, the two potential candidates being St Columba and Saint Máedóc of Ferns. If the former, then a religious house would have been established here in the mid-sixth century, if the latter then the date would be somewhat later. In any case, not a lot now remains to show how important this monastery had once been; at its height, Drumlane was the richest ecclesiastical establishment in this part of the country. The church is thought to be mid-12th century and in the aftermath of the Reformation continued to be used for services by the Church of Ireland until 1821 when a new church was built and this one unroofed. The adjacent truncated round tower, probably 11th century, is missing its upper section and now rises 38 feet.
It is believed that both Saints were involved in Drumlane and at two different stages. The buildings that are seen at Drumlane are mostly likely built later than either Saints time and funded by the O’Rourkes as Kings of Breifne. At that time the Kingdom of Breifne streatched from Sligo to Kells, Co. Meath so Drumlane would have been a centre point. The Kingdom of Breifne is roughly the Diocese of Kilmore as we know it today.