In the early autumn of 1966, photojournalist Ernie Husson was in the village of Aberfan, covering a story with the head teacher of Pantglas Junior School.
Parents had complained that their children were having to walk across a "sea of slurry" which had come down from a spoil tip above the coal-mining village in what is now Merthyr Tydfil county.
Within weeks, on 21 October, Mr Husson was back in Aberfan.
The trickle from the spoil tip which he had been reporting on had turned into an avalanche, directly hitting the junior school.
Miss Jennings, the head teacher who he had interviewed, was one of the 144 people killed in the disaster - 116 of those were children.
For Mr Husson, who is now retiring as a press photographer and journalist at the age of 76, the memory of Aberfan is still painful: "I was the first photographer into Aberfan.
"I was there in the first 15 minutes as I only lived three miles away. I had a call from the junior photographer in the office, who rang me and said the school roof had come down. My immediate reaction was 'that would make a great front page photo for the South Wales Echo'."
But the seriousness of the event became clear to Mr Husson as he made the short trip to the village.
"As I drove towards Aberfan I realised this was something bigger than just a front page picture because of the number of ambulances coming out of Aberfan and the amount of emergency vehicles going into Aberfan."
The situation was far worse than Mr Husson had expected. After days of heavy rain, tonnes of waste, earth and slurry had hit the school at 09:15 in the morning, shortly after morning assembly.
By 23:00 that evening, Mr Husson was still in Aberfan when Prime Minister Harold Wilson arrived.
Mr Husson said: "He looked at the press call I was part of and he smiled. I'm told that I said to the prime minister, 'This is no laughing matter, sir'."
Even after giving the prime minister a stern dressing down, Mr Husson said the enormity of the event still had not quite hit him.
"After the prime minster had gone, my editor said to me, 'You're going home you need some rest'. I went home but I couldn't sleep and I got up about 06:30 and went back into Aberfan.
"Someone offered me a cup of tea and I heard on the Welsh news about Aberfan and it was at that time I broke down.
"I couldn't talk about the Aberfan disaster for about 20 years after."
Mr Husson left Thompsons news agency less than two years after Aberfan, moving to Llandrindod Wells in Powys.
He spent the subsequent 52 years covering anything and everything in mid Wales as a freelance photographer and journalist for the three local papers based in the area.