He is often known as Constantine I in reference to his place in modern lists of Scottish monarchs, but contemporary sources described Causantín only as a Pictish king.

Originally simply a list of kings with reign lengths, the other details contained in the Poppleton Manuscript version were added from the tenth century onwards.

[2] The earliest genealogical records of the descendants of Cináed mac Ailpín may date from the end of the tenth century, but their value lies more in their context, and the information they provide about the interests of those for whom they were compiled, than in the unreliable claims they contain.

[5] If the sources for north-eastern Britain, the lands of the kingdom of Northumbria and the former Pictland, are limited and late, those for the areas on the Irish Sea and Atlantic coasts — the modern regions of north-west England and all of northern and western Scotland — are non-existent, and archaeology and toponymy are of primary importance.

[8] The following year, having obtained tribute from the East Anglian King Edmund, the Great Army moved north, seizing York, chief city of the Northumbrians.

[9] The Great Army defeated an attack on York by the two rivals for the Northumbrian throne, Osberht and Ælla, who had put aside their differences in the face of a common enemy.

Archaeological evidence suggests that Dumbarton Rock was largely abandoned and that Govan replaced it as the chief place of the kingdom of Strathclyde, as Alt Clut was later known.

[16] King Artgal of Alt Clut did not long survive these events, being killed "at the instigation" of Causantín son of Cináed two years later.

[21] In 877, shortly after building a new church for the Culdees at St Andrews, Causantín was captured and executed (or perhaps killed in battle) after defending against Viking raiders.

William Forbes Skene reads the Chronicle as placing Causantín's death at Inverdovat (by Newport-on-Tay), which appears to match the Prophecy of Berchán.