The Cambrian colliery lost 64 men in two separate explosions 60 years apart
Forty-five years to the day since Wales' last major underground mining disaster, survivors of the Cambrian Colliery explosion and relatives of the 31 miners who lost their lives will gather on Monday at the site of the former pit in a service of remembrance.
At 1pm on 17 May 1965, number one pit was shaken by a blast which could be felt for several miles around, when an electrical spark ignited trapped methane in the seam.
Bill Richards was on duty that morning at the mine in Clydach Vale, near Tonypandy in the Rhondda.
"That day I was working in number four pit, so I suppose I was always away from the immediate danger," he said.
"At about half past 11, I had a call to go back above ground, because the manager wanted to see me.
"When I got to the top, he said, 'I want a word with you. I've got to go down number one to sort out some problem with the machinery, but make sure you don't go home until I've spoken with you.'
"I never did find out what it was he wanted, because an hour and a half later, he and 30 other men were killed by the gas explosion."
Ernie Breeze, manager of the Cambrian colliery, died in the 1965 blast
An official inquiry concluded that methane had built up in the shaft after the ventilation system had been breached, allowing fresh air to by-pass the seam, and travel directly from the intake vent to the outlet.
The spark which ignited the gas came from a faulty switch which electricians were trying to repair.
Following the explosion a number of important safety recommendations were implemented across the south Wales coalfield, meaning that Cambrian would be the last such underground disaster.
But what frustrated and upset families, was that lessons had failed to be learned from a near identical explosion at the colliery, 60 years before in March 1905.
On that occasion 33 men died, a death-toll which would have been even greater, were it not for the fact that the explosion occurred during the change over of shifts.
The 1905 blast was so strong that it blew the cage lift right up the shaft, and off the end of the winding gear.
Yet no significant safety improvements happened between then and the 1965 blast.
With most of the miners coming from the tiny community of Clydach Vale, which has a population of just 3,000, Mr Richards says the effects of their lost generation can still be felt today.
"I got out of Cambrian not long after that," he said.
"Not so much because of the explosion, but because I could see which way the industry was going.
Bill Richards worked at Cambrian colliery at the time of the explosion
"Afterwards I ended up running a carpet shop, and every now and again, right up until my retirement, I had people come in asking, 'Mr Richards, did you know so-and-so?' When I'd say 'yes', they'd ask me, 'Did my husband used to talk about me?' or 'What was my dad like?'
"In the end I dedicated part of my window display to a sort of miniature museum for the families of Cambrian, just to try and share with them what I knew about their men."
The service takes place on the spot above where the explosion happened and a minute's silence will be held.