Sorry, this should have been posted yesterday.
On This Day: Blast kills 266 coal miners and rescuers at Welsh pit
Most of the victims remain entombed 2,600ft underground after a shot blast to extract coal is thought to have ignited gas at the pit near Wrexham, north Wales
Only 11 bodies were ever brought back to the surface and just six of the night-shift workers survived the inferno in the shaft, which was notorious for its poor air quality.
Three rescuers, who had rushed to the mine from a nearby colliery, were among the dead after being gassed following the 2am explosion that fateful Saturday morning.
Charles Harrison, 15, was the youngest victim of the disaster, which sparked fury after bosses escaped criminal prosecution despite breaching eight safety rules.
The oldest to die was 68-year-old Edward Wynn, who like the others had been trapped 1.3 miles from the bottom of the shaft as fire engulfed the mine.
Harold Bent, who was a 21-year-old miner at the time, told the Wrexham Daily Post in 2004. "There were sheets of flame all the way across. You couldn't get beyond it.
"You couldn't dowse it and that's where the men were stuck, trapped down there."
A British Pathé newsreel filmed worried women and children outside the pithead, where many waited three days until the hopeless search was called off.
Many of the families learned of the disaster from the few survivors, who were forced to make their own way home into the nearby village of New Broughton.
One of them was Cyril Challoner, whose wife Irene remembered: "At 5am my husband came home on his bike.
"He rang the bell and I thought, 'Oh, he's home an hour early'. He said: 'There's been a terrible disaster at the pit.'
"Then he passed out - just collapsed."
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Further explosions and a lack of firefighting equipment and water hampered the rescue bid.
A subsequent inquest was unable to establish the cause of the explosion, partly because the mine's owners refused to let inspectors view the sealed off shaft.
But the coroner criticised the mine for failing to take dust samples and breaching other safety regulations in a bid to turn the mine back to profit.
Yet, to the anger of families Labour party politicians and trade unionists, no criminal charges were ever brought.
The bosses were later sued in a civil court, but despite being found to have breached eight coal mine safety regulations, the manager William Bonsall was fined just £150.
The Gresford Disaster gave rise to a popular miners' song, which includes the lyrics: "Down there in the dark they are lying/They died for nine shillings a day/They have worked out their shift and now they must lie/In the darkness until Judgement Day."
The author is unknown, although it is thought to have been penned by John Williams, a rescuer who dragged a dying man 40 yards despite being severely poisoned himself.
The aftermath also led to calls to nationalise Britain's pits.
They eventually were in 1947 after Labour's post-war landslide election victory - but privatised again by the Tories four decades later.
The deadliest mining disaster in British history occurred in 1913 when 439 men were killed after a gas explosion at Senghenydd Colliery near Caerphilly, South Wales.