As much as i'd like to see Avebury restored to something like its last phase it'd have massive implications for health and safety, top of bank to bottom of ditch, 50 ft or more, little Tommy's mum, drunken revelers straight on the phone calling "compo lawyers for u" etc, fences erected, warning signs allover plus the labour of a fingertip excavation of the spoil.
Hmmm, might just be best leaving well alone imo. : P