M. de Dunblan is the way the first known Bishop of Dunblane is written in a copy of a papal bull of Pope Adrian IV preserved in England; the bull dates to 1155.Cockburn, Medieval Bishops, p. 6; Dowden, Bishops, p. 193; Watt & Murray, Fasti Ecclesiae, p. 99.
The papal bull was addressed to the bishops of Scotland ordering them to submit to the metropolitan authority of the Archbishop of York; the copyist made two other mistakes in the initials of bishops, so it is not totally reliable.Cockburn, Medieval Bishops, p. 6; Dowden, Bishops, p. 193.
Cockburn speculated that M. might stand for Máel Ísu;Cockburn, Medieval Bishops, p. 6 it is very unlikely that M. was a mistake for La., standing for Laurence the successor of M. at Dunblane.Dowden, Bishops, p. 193, n. 1.
Notes
References Cockburn, James Hutchison, The Medieval Bishops of Dunblane and Their Church, (Edinburgh, 1959) Dowden, John, The Bishops of Scotland, ed. J. Maitland Thomson, (Glasgow, 1912) Watt, D. E. R., & Murray, A. L., Fasti Ecclesiae Scotinanae Medii Aevi ad annum 1638, Revised Edition, (Edinburgh, 2003)