Whether Clovelly Dykes was still in use as a livestock shelter by the time of Arthur is not clear, certainly, exports were still an important part of the flourishing economy of the region; but what can't be disputed is whether the earthen banks of Clovelly Dykes stood in the time of Arthur. They are still imposing today.

People lived in the huts within the ramparts.

This is the base of a mounted strike force.

The exits are downhill, and on the opposite side from the obvious approach. 

Some parts are protected by three rings of earthworks, other parts by only one. 

Why?

 Because the occupants of those parts aren't supposed to be in the fort if it is attacked,  they should be outside mounted and armed.

This was the military and administrative heart of Arthur's Britain.

This was Camelot