Before Charlemagne came the Merovingians, Mayors of the Palace until Pope Stephen acknowledged Pippin as Ruler of the Franks.
Charlemagne’s anniversary coincides with the Battle of Clontarf. He died in 814. He had defeated the Saxons in the 780s and enforced their conversion to Christianity, defeated the Lombards and confronted the Muslims in Spain in the same decade. The Viking threat from the north would plague his successors. The new (‘Holy Roman’) Empire north of the Alps, a Christian empire, was sealed on Christmas Day in 800 when the Pope crowned Charlemagne in St Peters.
The division of the empire followed his death and then came the first of the Ottonians, Henry the Fowler (919-36), who re-established the Empire in the East Frankish Kingdom, which did not include the area of modern France included in Charlemagne’s empire.
Ottos I, II and III came next – and then Henry II who was there at the time of the Battle of Clontarf.
Brian Boru desired the same kind of recognition from Armagh as the Ottonian emperors desired from Rome. In 1005 Brian deposited 20 ounces of gold on the altar at Armagh; he guaranteed all the dues and rights of the Church. Armagh is to Brian what Rome is to the Ottonian emperors. The Book of Armagh has Brian as ‘Imperator Scotorum’ (Emperor of the Irish).
The Annals of Clonmacnoise state that after Clontarf, Donnchadh, the son of Brian brought the Crown of Ireland to Rome, to expiate his having murdered his brother. There are echoes here of the Donation of Constantine, when the Pope is said to have conferred temporal jurisdiction on the first Christian Emperor: that jurisdiction covered the islands, including Ireland.