The church of St Michael is sometimes listed under Glassonby and sometimes under Addingham, as the medieval church of Addingham was destroyed by the River Eden at an unknown date, and a new church built closer to the village of Glassonby, probably in the 16thC. but registers of the church go back only to 1602. The village of Addingham, itself, no longer exists. There are older carved stones used in the church structure which are thought to have come from the earlier church. Alterations were made in 1786 and 1898. In 1786, it was decided that a W porch be built and the N doorway filled in. The roof of the vestry was raised in 1898. Possibly at the same time, but almost certainly after 1840, the S porch was built, forming a new entrance into the church. This was likely carried out when the 18thC. W porch was taken down. Built into the S porch gable is a voussoir carved with chevron, and built into the N gable of the vestry is a voussoir carved with beakhead. These are the only known stones of Romanesque form. A number of Anglo-Saxon stones survive, most of which are known to have been recovered nearby from the River Eden and its bank.

Domesday Book did not cover this part of England. Glassonby and Addingham both lay in the ward of Leath, an eastern division of Cumberland. In the Sheriff’s Return of 1212 (Reg. of St Bees, p. 530), William of Ireby held Glassonby with the daughter of Odard by the gift of King John. Her ancestor, named Hildred, had been given Glassonby, along with Gamblesby, by King Henry I, which passed to her when the male line ended. Following the deaths of William and his wife, the patronage of the church was held between two daughters, but during the reign of King Edward I, it was granted to the priory of Carlisle (Nicolson and Burn, p. 450). Bishop Halton of Carlisle presented Robert de Scardeburgh to the church of Addingham in 1296. Christopher Seton inherited the manor of Glassonby, but it was forfeited to the crown when he was executed in 1306. It then went to the Dacres, who held it until the early 18thC.

No documents have been found which concern the two voussoirs and their re-use, and there is no record of when the S porch was built. It is thought to have taken place sometime after 1840, as an engraving showing the church at that time shows neither a S doorway nor a porch.