Fair enough. Not one I'm familiar with.
There's some fantastic drawings in Leslie Alcock's book "Arthur's Britain", which are repeated in David Nicolle's "Arthur and the Anglo-Saxon Wars". Alcock excavated the hill fort at South Cadbury and discovered the Sub-Roman gateway there. Wrote several books about it, many of which you can pick up for a song and are really useful resources for the period.
Found this browsing about, to give you an idea what I mean:
