Surviving Aberfan: Teacher Hettie Williams remembers pupils
Fifty years ago 116 children and 28 adults were killed by a roaring avalanche of coal waste in the mining village of Aberfan.
Coal waste dumped in huge tips on the mountain above the village started to cascade down, becoming an unstoppable and deadly force.
It crashed into Pant Glas Junior School and houses directly below the tips, causing death and destruction.
Teacher Hettie Williams, then 21, had a classroom at the front of the school for her first year class.
Mrs Williams recalled how she helped set up a school, along with the three other surviving teachers, at the local community centre for the children who had survived the disaster.
Surviving Aberfan is on BBC One Wales at 21:00 BST on Monday, October 17