A Brythonic kingdom of the post-Roman 'Old North' centred on the fortress of Alt Clut (Dumbarton Rock) on the River Clyde, possibly descended from the Damnonii; its 5th-century existence is corroborated by St Patrick's letter rebuking its king, Coroticus, for raiding Irish Christians.
After the sack of Dumbarton by a Dublin Viking fleet in 870, the kingdom's centre shifted and it re-emerged as an expanded 'Strathclyde'/'Cumbria'; it was eventually absorbed into the Kingdom of Alba/Scotland in the 11th century.
The atlas holds 5 border frames for Kingdom of Strathclyde (Alt Clut) — the shape you scrub through changes in 410 · 500 · 527 · 653 · 843.
Covers the Old North British kingdoms including Alt Clut/Strathclyde.