Fred the Head

David Nathan, an off-duty officer, was walking near an abandoned flint mill in Burton-on-Trent, Staffordshire, in an area accessible by a locked gate or a long walk down a narrow lane. He tripped on what looked like a bag of cement poking up from the ground but, on closer examination, found it was the top of a skull.

Who were they and what would they discover when they were dug out?