Just looking at the TMA posts for this one. Couldn't help but laugh at the plethora of photos of a bench mark, especially the idea that it could be a carving almost contemporary with a Bronze Age circle.
You'll be very excited to learn that there is an online database of benchmarks and an activity known as "benchmarking". The OS equivalent of trainspotting, presumably.
http://www.bench-marks.org.uk/
:-)