They crawl under a mountain to keep the world's lights on.

The method is called room and pillar, and it predates electricity itself. Miners undercut the seam with picks, drop the coal in slabs, and leave columns of it standing to carry the mountain above them. The roof between those pillars rests on pit props, tree trunks cut to length and wedged in by hand.

A steel winch cable hauls every cart up the incline, and the men ride the same cars down to the face.

Coal generates a third of the planet's electricity, and 7 out of every 10 tons of steel are still made with it.

A hundred and fifty years of method. One cable back to daylight.

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