Re-discovered recently, they are an extraordinary testament to the dogged ingenuity, bravery and skill of those who created them. In places, the chalk walls still show the friction marks where the passing of men left the rock smooth. In others, soot-trails give away the places where candles were lodged.
While we were there, further down, accessible only by winch, were a BBC News crew, filming a quiet memorial ceremony for two miners lost in October 1915, which would be going out on the 6 o'clock News that day. We could hear the voices - historian Peter Barton among others - rising up the shaft.