Ah, I see. This is quite fascinating stuff. One issue is, who would have had tribal control? The Cornovii were a fairly poor pastoral tribe, but it lies in their territory. The Dobunni, who in my conjecture constructed Wychbury, could be responsible though, because they would have wanted a stronghold on the Severn to alert them to any attack from the even more hostile Ordovicians, who were noted raiders even after the Roman occupation, the Vikings found that the same site conduced to their needs much later on, and i think had their original fortress downstream of Bridgnorth, at Quatford. Trade on the river must have been brisk, even back then. Its also on a line of sight to the Clee hills, and to the Wrekin, so i guess would have been a useful signal station, even if it wasn't a succesful redoubt...