For over a decade, black greasy sludge washed down the streets of a Welsh mining village every time it rained. The local council sent letters. The danger was in plain sight. And the men at the top of the National Coal Board simply looked the other way.

This episode is a deep dive into the official tribunal records of the Aberfan disaster of October 21, 1966, when a liquefied mountain of mining waste killed 144 people, 116 of them children. It is a profound lesson in regulatory failure, corporate self-protection, and the staggering injustice that followed.

• How tip seven was built directly on top of springs marked on maps since 1874, violating the NCB's own safety rules
• The fatal physics of tailings, fine waste that turns to quicksand when saturated, twice the density of water and moving at 21 miles per hour
• The chi ...