Archdeaconry of Lothian  The Archdeaconry of Lothian, located in modern-day Scotland, was a sub-division of the diocese of St Andrews, one of two archdeaconries within the diocese and in essence that part of the diocese which lay south of the Forth. The Lothian archdeaconry was headed by the Archdeacon of Lothian, a subordinate of the Bishop of St Andrews. In the medieval period, the Archdeaconry of Lothian contained three deaneries: Linlithgow, Haddington and Merse.