This territory, as far as Malory is concerned, seems to rate mention only in the title of Duke Eustace of Cambenet (Escant). According to the Vulgate, Cambenic is a rich and prosperous city, and the name of its duke is Escan (Escant). Cambenic seems to be on or near the Severn River, for when King Lot and his sons helped Duke Escan, they drove the Sesnes into the Severn.
A little river running through Bresquehan Forest formed the boundary between Norgales and Cambenic. This suggests that Cambenic was the southern half of Shropshire, possibly also including Herefordshire or the northern part thereof.
I assume that Escan is to be identified with Eustace and Cambenic with Cambenet. To save both names, Cambenet might be applied to the whole territory of the dukedom and Cambenic to its principal castle-city.
Cambenic | The Legend of King Arthur