Precariously-perched planning frames

I expect it was really the emergence of the Iron Age rampart wall from the tumble that caught Dr Ferris's eye, when he took this photograph in 1979, looking at the southern edge of cutting AXV from the east.  But it is interesting to note the ingenuity that was required to balance the 2 m square planning frame on steel pegs hammered into the cutting when the land surface, because the narrowness of the apex of the rampart, was not broad enough to support the frame on its own.