Will Millard goes in search of the lost and hidden locations from Wales’s coal history. Wales once led the world in the production of coal, exporting the black gold to the four corners of the Earth. Since that industry collapsed, much of the infrastructure has been destroyed, forgotten or hidden away. Will goes in search of those final pieces of coal history. He visits one of the country’s last coal mines, where they have dug up centuries-old workings, explores the abandoned buildings of some of South Wales's forgotten collieries and lands on an island that was responsible for wrecking hundreds of coal ships.