Historia Brittonum “The History of the Britons” was an influential document about early history in Britain, being one of the only texts about the subject. Given the role that it played, it is little surprise that a version of it was translated into Gaelic, with some additions, and called Lebor Bretnach “the British Book,” probably in the late 11th century. It has also recently been argued that this translation/adaption of the book was done by scholars in Scotland, rather than in Ireland, as previously assumed.
The following is a translation by Michael Newton of an extract from the edition in A. G. Van Hamel, ed. Lebor Bretnach: The Irish Version of the Historia Brittonum ascribed by Nennius. Dublin: Stationary Office, 1932.
§ 14. Of the Travels of the Gaels. Gaelic scholars give the following account of the adventures of their leaders in ancient times. There was a certain [Scythian] nobleman who had been banished out of the kingdom of Scythia who was in exile in Egypt. After the children of Israel passed through the Red Sea and [the Pharaoh] Forann was drowned along with his army, the Egyptians who survived banished this nobleman, because he was the son-in-law of Forann who had drowned.
Afterwards these Scythians went on a long journey: they went into Africa, to the altars of the Philistines, to the wells of Salmara, between the Rusicadum and the Azariea Mountains, across the River Malvam, through the Mediterranean to the pillars of Hercules, beyond Tyrrhenian Sea to Spain. They inhabited Spain until thousand and two years had passed since Forann was drowned in the Red Sea.
Then the sons of Míl went to Ireland in thirty boats, with thirty couples in each boat. The king, Donn, was drowned at Taigh Duinn [the house of Donn]. Until that time Ireland was ruled by three goddesses named Fotla, Banba, and Éire. The sons of Míl, however, conquered them in three battles and afterwards took the kingdom.
The two sons of Míl started arguing hotly between each other about the kingdom until their judge Amergin of the white knee, also the son of Míl, settled the dispute. He was also their poet. This is the settlement which he made: Ireland was to be divided into two halves; Éber took the northern half and Éremon took the southern half. Their descendants still live in this island.
§ 15. The Britons took possession of this island [Britain] in the third age of the world, but the Gaels took possession of Ireland in the fourth age of the world. At this same time the Picts [Cruithnig] took the northern region of Britain. The Dál Riata came in the sixth age and took possession of Pictish territory and at that same time the Saxons conquered part of the island from the Britons.