The Aberfan disaster

At 9.30 on the morning of October 21, 1966, tragedy struck the small Welsh mining village of Aberfan, near Merthyr Tydfil (what a wonderful language). A slagheap collapsed, engulfing the village school.

The disaster left 1441 dead.
It virtually wiped out an entire generation of schoolchildren.

The children were gathering for morning assembly when the landslide began. Gaynor Minett, an eight-year-old at the school, remembered four years later:

It was a tremendous rumbling sound and all the school went dead. You could hear a pin drop. Everyone just froze in their seats. I just managed to get up and I reached the end of my desk when the sound got louder and nearer, until I could see the black out of the window. I can't remember any more but I woke up to find that a horrible nightmare had just begun in front of my eyes.
In a matter of seconds both Pantglas Infants' and Junior School, together with surrounding buildings, were buried under two million tons of mine waste, rocks and sludge. From midday the school would have been empty for the half-term holiday.

Rescue work went on all day and throughout the night as more than 2000 policemen, firemen, civil defence workers and volunteers tunnelled through 15 meters of slag to recover bodies and search for survivors. Policemen and reporters burst out in tears as the first young bodies were carried out of the mud. By then the full extent of the tragedy was clear to everyone. According to eyewitnesses, mothers and grandmothers scrabbled at the rubble with their bare hands. The prime minister and the Duke of Edinburgh flew to the scene to offer their condolences.

A hundred thousand people gathered on October 27 when the first funerals took place. Eighty-one small coffins were lowered into two long trenches in the hillside cemetery. The Tribunal of Inquiry concluded after a 76-day session that the National Coal Board was guilty for neglecting earlier expressed safety warnings over the slagheap:

The Aberfan Disaster is a terrifying tale of bungling ineptitude by many men charged with tasks for which they were totally unfitted, of failure to heed clear warnings, and of total lack of direction from above. Not villains but decent men, led astray by foolishness or by ignorance or by both in combination, are responsible for what happened at Aberfan. (...)
Blame for the disaster rests upon the National Coal Board. This is shared, though in varying degrees, among the NCB headquarters, the South Western Divisional Board, and certain individuals. (…) The legal liability of the NCB to pay compensation of the personal injuries, fatal or otherwise, and damage to property, is incontestable and uncontested.

1 There seems to be some inconsequence between sources when dealing with the number of casualties (144 or 147). Thanks Gritchka.