twin citadel at Dumbarton Rock, strategically located at the confluence of the Clyde and Leven rivers, in AD 870 after a four-month siege. This fortress, known as Alt Clut or Alt Clud in the local Northern Brittonic (Cumbric) language, was the centre of an ancient Brittonic kingdom.

With the king of Alt Clut, Artgal, either killed or enslaved by the Vikings, Govan and Partick,