Hachures on OS maps typically indicate sloped or disturbed ground, the kind of notation that can suggest anything from an ancient earthwork to a natural hollow, and for decades this particular feature carried the faint ambiguity that such markings tend to invite. When someone finally went to look in 1984, the answer turned out to be thoroughly unglamorous: a large, disused gravel pit, dug at some point after 1700 and long since abandoned by the time anyone thought to investigate it formally.