Formation and Exile in Ireland
Egbert was born about 639 in Northumbria to a noble family and first entered monastic life at Lindisfarne. Seeking further study, he traveled to Ireland, where his acquaintances included Chad of Mercia, and settled at the monastery of Rath Melsigi in what is now County Carlow.
In 664 a devastating plague swept through his community. Most of his Northumbrian companions, among them Aethelhun, died of it, and Egbert himself fell ill at the age of twenty-five. Facing death, he vowed that if he recovered he would live as a perpetual peregrinus — an exile for Christ dedicated to penitence, prayer, and fasting — and would never return permanently to Britain. He recovered and kept the vow for sixty-five years, until his death at ninety.
Organizer of the Frisian Mission
As a priest, Egbert became instrumental in organizing monastic communities for missionary work among the pagan Frisians. Dissuaded by a vision from going himself, he instead sent and arranged for others: he dispatched Wihtberht to Frisia first, and afterward helped set in motion the missions of Willibrord, Adalbert, and Swithbert.
His concern for the affairs of his homeland is also recorded: in 684 he attempted, without success, to dissuade King Ecgfrith of Northumbria from launching a military expedition into Ireland.
Iona and the Roman Reckoning of Pascha
In 697 Egbert attended the Synod of Birr in County Offaly, at which the Cain Adomnain — the 'Law of Innocents' protecting non-combatants — was ratified. The synod was convened in the circle of Adomnan, Abbot of Iona, placing Egbert among the leading churchmen of the day roughly two decades before his own move to that island.
Around 716 Egbert relocated to Iona, the monastery founded by Columba in 563, where he advocated the adoption of the Roman calculation of Easter in place of the older Celtic practice. He worked among the monks there from 716 until his death in 729. His arrival coincided with a period of upheaval over the Paschal question — Iona's monks were expelled from Pictish territory by King Nechtan in 717 amid the same controversy over Roman reform.
By tradition, Egbert died on Iona on April 24, 729, at the age of ninety — on the first day the community there formally observed Easter according to the Roman reckoning he had urged upon them.
Veneration
Egbert is venerated as a saint and confessor. His feast is kept on April 24, the observance reflected in the anchor commemoration and in Western usage; some Eastern Orthodox traditions have also commemorated him on December 23 (December 23 O.S. / January 5 N.S.).
OrthodoxWiki does not yet carry a dedicated article on Egbert, and the OCA calendar for April 24 lists chiefly Eastern saints rather than Egbert, whose veneration is concentrated in the Western Orthodox and Celtic traditions.