Everybody in the UK active on social media who was alive at the time seems to be posting or tweeting where they were at the time of the Aberfan catastrophe, so here is my contribution. I cannot remember exactly where I was except that it would have been in south London, because there were other momentous events in my life taking place at the time. The Centralised Licensing Project (to become DVLA) had just been set up and I was preparing to get married. I would have learned of Aberfan from BBC Radio (it would be several years before we acquired a TV set). One thing I do remember is the thought that it had been a disaster waiting to happen, something the Guardian leader-writer of the following day also intuited:
How could it happen? A heap of waste, a man-made hill, dissolves in the rain and suddenly engulfs a school. South Wales is a land of slag-heaps. Its people live in their shadow. Why did this one move? The Coal Board must find out, and the answer may not be soothing. Miners are not careless men, but in some way had not forseen the waste they had piled round Aberfan had become unsafe. South Wales will be a restless places until we know why.
Meanwhile mere words can do nothing to help.
The Welsh, who are used to tragedy, have now suffered their worst. The pits themselves do not kill children.
A disaster which overwhelms a school is a disaster of a special type. In ten minutes a community has lost something like half its children. Their absence will haunt their valley for sixty years to come. No amount of sympathy can fill a gap like that.
[...]This disaster was not natural, it was man-made. Aberfan is one of scores of communities in South Wales which huddle at the foot of slag-heaps. It is idle to pretend that an exceptionally wet October could be the only reason for yesterday's disaster; Wales is accustomed to heavy rain. There must have been other reasons too, connected with the way the heap was built, or was allowed to grow, and with the gap that was built, or was allowed to grow, and the gap that was left between the heap and the village. These are things that can be controlled. There must be a safe way for the Coal Board to get rid of its waste. There must be a way of ensuring that yesterday's tragedy is not repeated.
As a Guardian reader at the time, I would have read and agreed with this. We eventually found out, in spite of Coal Board obfuscation, that the Aberfan disaster was indeed effectively genocide or at least corporate manslaughter.Though the slag-heaps have gone, there is no evidence that the corporate (both private and public) mindset has changed.
The only other firm memory is of my late father-in-law returning from a photographic trip through Wales the following spring. He related how he had passed through a village which was unnaturally quiet and found out only later that it had been Aberfan.