Originally centred in the valley of the River Clyde, this realm appears to have undergone considerable southward expansion in the ninth or tenth century, after which it increasingly came to be known as the Kingdom of Cumbria.

Owain may have represented the Cumbrians in the tripartite alliance with the kingdoms of Alba and Mercia, assembled by Æthelflæd, Lady of the Mercians in the second decade of the tenth century.

[11] The kingdom's new capital may have been situated in the vicinity of Partick[12] and Govan which straddle the River Clyde,[13] and the apparent inclusion in the realm's new hinterland of the valley and the region of modern Renfrewshire may explain this change in terminology.

[37][note 5] If this record is indeed accurate, one possibility is that, whilst the Scots focused upon Argyll and the Hebrides, the Cumbrians could have concentrated their efforts against the Scandinavian colonies in the Solway Firth.

[41] Another candidate is Sitriuc Cáech, an Uí Ímair kinsman of Ragnall, who is stated by the same source to have seized the kingship of Dublin before the attack.

[44] In the year of Æthelflæd's death, Ragnall and the Scots fought the bloody but inconclusive Battle of Corbridge, a clash attested by sources such as the fifteenth- to sixteenth-century Annals of Ulster, the ninth- to twelfth-century Chronicle of the Kings of Alba, and the tenth- or eleventh-century Historia de sancto Cuthberto.

The conflict appears to have been associated with Custantín's attempt to reinsert the exiled Northumbrian magnate Ealdred, son of Eadwulf, into western Northumbria.

[48] In 920, the "A" version of the ninth- to twelfth-century Anglo-Saxon Chronicle alleges that Æthelflæd's brother, Edward, King of the Anglo-Saxons, gained the recognition of overlordship from Custantín (albeit not identified by name), Ragnall, the sons of Eadwulf (seemingly Ealdred and Uhtred), and an unnamed "king of the Strathclyde Welsh" ("Stræcledweala cyning")[50]—a monarch who may well be identical to Owain himself.

[54] Despite the chronicle's claim of Edward's received submission, there is reason to suspect that the event was more a negotiation of sorts—perhaps an agreement concerning the recent reorientation of the political map.

[67][note 8] Whatever the case, Owain's involvement may have concerned support rendered to Gofraid ua Ímair, a man who temporarily seized the kingship of York in 927 before being driven out within the year by Æthelstan.

[74] Certainly, Gesta regum Anglorum states that Æthelstan summoned the Cumbrian and Scottish kings to the assembly after having forced Gofraid from York into Scotia.

[77] In fact, the contemporary Latin poem Carta, dirige gressus seems to not only corroborate the meeting itself,[78] but may further evince the assembly's importance to the Cumbrians.

Specifically, the poem states that Custantín hastened to Bryttanium in order to render his submission, and it is possible that this terminology refers to the Cumbrian realm (as opposed to the entire island of Britain).

[82][note 9] Whatever the case, Æthelstan's assembly in the north, and another convened near the Welsh border not long after, marked a turning point in the history of Britain.

[96] According to Chronicon ex chronicis the King of Alba had indeed broke a treaty with Æthelstan, and that the former was forced to give up a son as an English hostage.

[98] Whether the invasion was unprovoked or orchestrated in revenge, it and another campaign directed against the Cumbrians eleven years later, could well have been utilised by the English Cerdicing dynasty as a way to overawe and intimidate neighbouring potentates.

As such, the English invasion of 934 could well have been punitive in nature, and its success may be partly exemplified by Custantín's appearance in the witness list of the September 934 charter, in which he is the first recorded subregulus amongst others.

[116] Æthelstan's attempt to incorporate the northern kings into an imperial subreguli system—an arrangement he had earlier initiated with the rulers of Wales—was interrupted before the end of the decade.

[124][note 14] Described by the Annals of Ulster as "a great, lamentable and horrible battle",[127] the English victory at Brunanburh was a resounding military achievement for Æthelstan.

[136] Although the Cumbrians are not specifically mentioned by the text,[137] it is possible that the composer chose to leave them out due to technical constraints regarding the piece's metre and structure.

[138] By leaving out the Cumbrians and Owain, the poem presents the opposing sides symmetrically: the West Saxons and Mercians—led by Æthelstan and Edmund I—versus the Scandinavians and Scots—led by Amlaíb and Custantín.

[139] Perhaps the Cumbrians' part in the conflict was overshadowed by the combatants;[140] or maybe the poem's composer merely regarded Amlaíb's supporters to be sufficiently represented by the Scots alone.