This hillfort at Cheddington was only rediscovered in 1973 from aerial photos, as its ramparts had been ploughed for so long. It's intervisible with Ivinghoe Beacon just a few miles to the east and could well have been occupied at the same time (people started living here in the Early to Middle Iron age*). From the bottom photo in the link below it seems that the hill continues to be an obvious spot in the landscape - visible from the road and railway (and most likely the canal too). http://cheddington.web-labs.co.uk/thevillage/photos/scenes/?textonly=on
Cheddington was called 'Cetendone' in the Domesday survey, which apparently means 'Cetta's Hill'.