There are two iron age forts/camps within 300 metres of each other on the hill apparently. On wednesday went past the Horton Camp near Chipping Sodbury,(which you put on TMA) did'nt take a photo, but that is a 5 acre site with I think a central boundary. Horton has a marvellous situation, Wales and the channel in one direction, White Horse at Cherhill in the other.. any way, there is also a longbarrow (partially destroyed) along the lane at Hawkesbury, on top of the hill there. Stantonbury and Littledown fort round Bath (we have 4 hillforts) has a central boundary, I reckon it is a human/animal barrier, but they must have been used as animal stockades all through the centuries as well.