Two entries with the name Gillomaur of Ireland.
Gillomaur of Ireland
Gillamaur, Gillamore, Guillamurius
The King of Ireland several generations before Arthur.
He allied with the Huns and Picts – led by Guanius and Melga – to invade Britain. Gillomaur’s Irishmen were driven out by the Romans, under Febus, and then “for good” by Constantine of Brittany.
Sources
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138
Roman de Brut | Wace, c. 1155
Brut | Layamon, late 12th century to mid-13th century
Gillomaur of Ireland
Colman, Guillamure, Gwylmar, Gwylomar, Villamus
The King of Ireland in the early days of Arthur’s reign. He came to the aid of the Scots and Picts, whom Arthur was fighting at Lake Lomond, but Arthur defeated him and sent him back to Ireland with a depleted army.
After pacifying the island of Britain, Arthur invaded Ireland and captured Gillomaur, forcing the rest of the country to surrender. As his subject, Gillomaur assisted Arthur in the invasion of Gaul and in the Roman War.
In Hughes’ The Misfortunes of Arthur, Gillomaur joins Mordred’s treason against Arthur and is slain at the battle of Camlann.
Sources
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138
Roman de Brut | Wace, c. 1155
The Misfortunes of Arthur | Thomas Hughes, 1587