There’s a dramatic change of atmosphere here, as the former railway line slices through a small spur of the hill. At this point we are literally walking through a cross section of the very material of the White Peak: Carboniferous limestone.
Run your hand over the surface of the rock. It can be highly variable across the White Peak but this is tough, top grade building material. Almost certainly the spoil from this cutting was used in one or both of the huge embankments on our route. The builders may indeed have deliberately carved through here to get at the high quality rock rather than take a diversion.