I have just found this excellent piece of historical detective work, on where Boudica's last battle might have been.
http://bandaarcgeophysics.co.uk/arch/bo ... stics.html
It appealed to me, because it's not orthodox history regurgitated, but based on (what seems to me to be) sensible reasoning based on military logistics, supplies and marching camps a day apart. Not least because Ogbourne St.George ranks as one of the very most likely places! But it might have been Hattie's Silchester, or Arthur's Mount Badon.
Anyway, my point is, what was true for your average Roman footsoldier was true for your megalithic tin-mover. You needed a safe place at the end of each day's slog to rest your weary feet and mules. You and the mules needed water and protection from whatever. Especially if you are enforcing Roman control over existing trade.
So - from the known map of known (and predictable) Roman Marching Camp sites, can we reverse-engineer where there must (for practical functional reasons) have been megalithic trade route enclosures as well?
See http://www.bandaarcgeophysics.co.uk/arc ... ps_uk.html