This group of people has a number of names including Ystrad Clud, Alclud, Alt Clut (Old Clyde) and Strath-Clota. This “kingdom” had arisen in post-Roman times and although it’s base was at Dumbarton Rock on the Clyde, its territory projected as far south as modern-day Cumbria.
Strathclyde would survive as an independent (although not hugely powerful) kingdom into the 10th and 11th centuries before it was subsumed by the Kingdom of Scotland.
The Northern Tapestry 