EINEON (fl. 1093), Welsh prince and warrior, son of Collwyn, played a great part in the famous legend of the conquest of Glamorgan by the Normans. His father and his elder brotner Cedivor seem to have been under-kings in succession of Dyved or of some part of it. In 1092 Cedivor died (Bruty Tywysogion, s. a. 1089, but cf. Freeman, William Rufus, ii. 78). His son Llewelyn and his brothers (B. y T.), his sons according to another account (Annales Cambriæ, s.a.l089), rose in revolt against Rhys ap Tewdwr, the chief king of South Wales, but were overthrown by him at Llandydoch. These discords gave easy facilities to the Norman marchers to extend their conquests in Wales. Next year Rhys was slain by the French of Brecheiniog. The conquests of Dyved and Ceredigion immediately followed. Thus far the history is authentic, but Eineon's name does not specifically appear in it. The legend now begins. Eineon, the brother of Cedivor, fled from the triumph of Rhys at Llandydoch to Iestin, son of Gwrgan, 'prince of Morganwg, who was also a rebel against Rhys. Now Eineon had been previously in England, had served the king in France and other lands, and knew well both William himself and his great barons. He proposed to Iestin to bring his Norman friends to the latter's help on condition of his receiving as his wife the daughter of Iestin and as her portion the lordship of Miscin. Iestin accepted the proposal. Eineon visited his English friends at London. He persuaded Robert Fitz-Hamon, whom we know in history as lord of the honour of Gloucester, and twelve other knights to bring a great army to the aid of Iestin. Rhys was slain by them in a terrible battle near the boundaries of Brecheiniog, at Hirwaun Gwrgan. With Rhys fell the kingdom of South Wales. The Normans, having done their work for Iestin, received their pay and returned towards London. They had hardly departed when Iestin, flushed with his triumph, treacherously refused Eineon his daughter's hand. Eineon pursued the retreating Frenchmen, explained to them his own wrongs and the general unpopularity of Iestin, and showed how easy it would be for them to conquer Iestin's dominions, since his treason to Rhys had so much disgusted the South-Wales princes that not one would afford him succour. The Normans were easily persuaded. Eineon meanwhile organised a Welsh revolt. They jointly spoiled lestin and Morganwg, but the Normans took the rich vale for their own share and left Eineon only the mountains of Senghenydd and Miscin, while the sons of Iestin were rewarded for their acquiescence in their father's fate by the lowland lordship of Aberavon. Induced by the victory of Fitz-Hamon, other Normans seized upon Dyved, Ceredigion, Brecheiniog. Thus the treachery of Eineon put all South Wales into the hands of the foreigner.
This full and elaborate story is first found in the 'Brut y Tywysogion,' first printed in the second volume of the 'Myvyrian Archaiology,' and afterwards with a translation by Mr. Aneurin Owen for the Cambrian Archæological Association in 1863. But the original manuscript of this 'Brut' is believed not to be older than the middle of the sixteenth century, and therefore not much earlier than Powels 'History of Cambria' (1584), in which the story of the conquest of Glamorgan also appears at length, varying from the above account in only a few details. There are here added, however, long pedigrees of the descendants of the 'twelve knights,' and most critical inquirers have agreed that the fertile invention of the pedigree-makers for Glamorganshire families is the original source of the legend. But there must be some nucleus of truth and some ancient basis for the inventors to have worked upon, for the conquest of Glamorgan is undoubtedly historical, though there is no direct account of it in any earlier authority. There is nothing in itself improbable in the story of Eineon, though there are slips in detail. If he had such great connections, why did he not use them to save his native Dyved from Rhys's assault? Rhys, too, was undoubtedly slain by Bernard of Neufmarché and the conquerors of Brecheiniog. Moreover it is absurd to suppose that after doing their work the Normans would have gone home again or needed Eineon's suggestion to turn their attention to the conquest of Morganwg. Obviously the expansion of the Norman arms from Gloucester into Morganwg was as natural as that of the expansion of the Shrewsbury earldom into Powys. But the quarrels and invitations of local princes were here, as in Ireland, a determining cause of their action; and Eineon's part in the conquest is too probable and typical for us lightly to reject the whole of his history. Some Welsh families profess to be descended from Eineon (Lewys Dwnn, Heraldic Visitations of Wales, i. 29, Welsh MSS. Soc.; for a full list see Clarke, Limbus Patrum Morganiæ, p. 131 et seq.)[Brut y Tywysogion, pp. 68-75 (Cambrian Archæological Association); Powels History of Cambria, pp. 119-27, ed. 1584, with the comments of Mr. G. T. Clark in his first paper on the 'Land of Morgan' in xxxiv. 11-39 of the Archæological Journal, and subsequently reprinted separately with the other papers on the same subject, and those of Professor Freeman in William Rufus. ii. 79-82, 613-15, note gg; cf. Norman Conquest, v. 820.]