Friday 21 October, 1966, began much like any other morning in the small mining village of Aberfan, near Merthyr Tydfil.
At Pantglas Junior School, it was the last day before half-term. 240 school children had arrived at the gates for a full day of lessons.
But just minutes into the school day, at around 9:15am, the unspeakable happened.
A slag tip on the mountainside behind the school gave way and 150,000 tonnes of slurry slipped downwards, hitting the school and the neighbouring houses with force.
David Evans, a resident of Aberfan, recalls the moment he first realised something had happened.
I was about to leave for work when I was asked by a neighbour who was in a state of panic if he could use the phone... I said yes of course, I said what's the matter? He was in a state of panic and he said that he'd heard that a house had collapsed in Moy Road.
David dialled 999 to alert the emergency services. But it wasn't until he stepped outside that the true scale of the disaster dawned on him.
I hadn't seen anything or heard anything... but I came [outside] and a lady ran past and she said to me "the school has gone, the school has gone". It didn't register... what did she mean?
An around-the-clock battle began to rescue those trapped by the debris. Firefighters, emergency services, miners, parents and local residents dug tirelessly, hour after hour, forming a conveyor belt of "bucket brigades" to help move the waste away quicker.
But by midday, hopes of finding more survivors began to fade.
144 people were killed. 116 of them were children.
A tribunal was set up a number of weeks later, to try to establish how such a tragedy could have occurred. Its findings, published the following year, blamed "bungling ineptitude by many men" who had failed to heed clear warnings.
Not villains but decent men, led astray by foolishness or by ignorance or by both in combination, are responsible for what happened at Aberfan.
Today, 50 years on, the victims of the Aberfan disaster rest in the village's cemetery, while the site of the former school is now a memorial garden.
But the events of that fateful day, and the lives that were lost, will never be forgotten.