GeoGraph - photograph every grid square

Having spent the last ¼ mile or so tunnelling under Sheffield station, the River Sheaf, which gives Sheffield its name, emerges from the bridge ahead of us and goes back underground below the camera. But it never again emerges: it is carried through another tunnel under the city centre and when it reappears ¼ mile or so north it immediately joins the river Don. See SK3587 : Sheffield: the Sheaf joins the Don.