Many of the people of Aberfan still cannot bring themselves to speak of it.
Forty years on from the disaster some parents, now in their seventies, still secretly hope their children will come home from school.
Others tell of the grief and trauma visited on their tiny community by the huge slag heap which slid from a hill above Pantglas junior school, killing 116 children and 28 adults.
Only 25 children survived the catastrophe. Now in their forties and fifties, many still speak of the nightmares and the psychological scarring that afflicts them. The name Aberfan remains synonymous with unspeakable grief about the death of children.
The morning of 21 October 1966 was a typically moist and misty day in the valley near Merthyr Tydfil in south Wales - although the sun shone further up the mountain. The children were in buoyant mood because it was the last day of school before the half-term holiday.
Assembly was shorter than usual. The children sang "All Creatures Great and Small" and then went off to their classes.
Just before 9.15am they heard a strange rumbling noise. The lights in their classes which hung on long wires from the ceiling began to sway. One teacher said it was probably thunder. In fact a 30ft wave of coal, mud and water was heading for the school. Already it had engulfed a farm cottage in its path, killing all the occupants.
Gaynor Madgwick, then eight years old, remembers that morning vividly. Her mother had to persuade her seven-year-old brother Carl to go to school. He had protested, saying it was not worth it because it was the last day before the break. Carl and Gaynor's sister Marilyn were killed.
"The first I knew there was something wrong was when I heard a horrific, terrifying rumbling noise getting louder and louder," says Gaynor. "People were frozen to their seats with fright. I tried to run to the door, but then I saw the black coming through the windows.
"I don't remember anything else until I woke up. I had been impaled at the back of the classroom. Underneath me were two boys who were dead; one was foaming at the mouth, the other's head was cut open."
She found a severed arm on her shoulder. "It was strange. I was convinced it was my brother's arm. He had been in the next classroom, and it gave me a feeling of peace to think it was him. I couldn't see or feel my legs. I think a radiator must have fallen on them.
"I sat there looking at everyone. We'd been engulfed in stuff that had the consistency of cement. It had steam coming off it. I picked up a book called Through the Garden Gate. It was full of blood, but I started to read it."
Eventually rescuers began to appear. "The first person I saw was my granddad. Then I started to cry. I never forgot the look on his face."
Later in hospital, she asked about her brother and sister. "My Dad said they had gone to heaven and my Mum started sobbing."
In common with many other survivors she did not talk about that day for years. "There was no counselling in those days and people assumed because we were children we were resilient, but we were suffering." When she was a teenager, however, Gaynor underwent psychiatric treatment - even then, neither she nor the town were ready. "That was humiliating. It was a stigma in back then."
The tragedy continues to have a devastating effect on those involved. "Some have died young, some have been constantly depressed. Some have been in and out of psychiatric hospital. One person has become a recluse. Most people have handled it by not talking about it, but I don't think that's the right approach," she says.
The writer Laurie Lee, who visited Aberfan a year after the disaster, later remarked that the surviving children were part of the "unhealed scar tissue of Aberfan". That is still true.
In Jeff Edwards' class, only four of the 34 children survived. Jeff, then eight, was saved because he was trapped in a pocket of air. "I remember waking up and there was a dead girl across my shoulder. Her face started to puff out, but one eye seemed to be sinking into her head. There were screams and shouts to begin with, but the sounds got less and less.
"When I was being rescued I remember saying that I wanted to take my felt-tip pens with me, but they said 'Bugger your felt tip pens', and I was thrown from one rescuer to another. I was finally taken out of the building at about 11 o'clock. I was the last one to come out alive.
"I was examined by doctors and wrapped in a red blanket. Even now in hospitals I shudder when I see them."
Jeff was treated for head and stomach injuries, but the real injury was the long-term psychological impact. "It can be very burdensome. It can close you down for a couple of days. I have to go to bed until it's over. I get irritable and depressed. You can get bouts of guilt for surviving while others were killed. But those seem to be the classic symptoms of anybody who has been involved in disasters."
Clearly Jeff still needs someone to explain to him why he survived and others died: "Many people can't talk about it. It upsets them too much. The huge emotional waves can be uncontrollable. Even after 40 years some people are still waiting for their children to come home."
Despite the emotional burden, Jeff went on from Pantglas to the London School of Economics and a City accountancy firm. He returned to the area to become an independent councillor, and eventually mayor of Merthyr.
At the time of the disaster, there were some 100,000 miners in south Wales, an area which relied heavily on the coal and steel industries. Today there are a few hundred miners left. Most of the pits - like Merthyr Vale colliery, which produced the Aberfan slag heap - have been "landscaped". One has been turned into a museum.
Pit closures under the Thatcher government ripped the heart out of the Merthyr area. At one stage nearly 30 per cent of the able-bodied were out of work, while other adults were registered disabled largely through industrial diseases.
With the help of regional grants the area has slowly picked itself up by its boot straps. Now the unemployment rate has dropped slightly, and these days the rivers and streams which once ran black with industrial waste boast trout and salmon. Heron and kingfishers are regularly seen where few birds would venture 40 years ago.
Aberfan was once the archetypal monochrome industrial village, with mountains stripped bare of deciduous trees to feed the furnaces of nearby ironworks and black patches of coal visible where grass struggled to grow. Now the hills are carpeted in Forestry Commission conifers, the village is brightly painted and cars are parked outside most homes.
And yet the Aberfan disaster still haunts this part of Wales. Apart from the deep emotional scars, there is a legacy which is causing considerable bitterness - although it is a word that local people prefer to avoid.
There is an unresolved conflict over reparation. A reluctant National Coal Board, which denied responsibility for the catastrophically unstable slag heap, was forced to pay compensation. Lord Robens, the board's chairman, claimed that his officials were unaware of the stream that ran through the tip and liquefied its contents so disastrously. The stream appeared on the Ordnance Survey map of the locality.
After much wrangling the sum of £500 was paid to those involved, and £1,000 to those who had lost one or more children.
A document released under the 30-year rule showed that the authorities in London felt that a more substantial sum would have destroyed the working-class beneficiaries because they would not be used to large amounts of money.
Aberfan had to pay £150,000 to get rid of the remaining parts of the slag heap out of a charitable fund to which people from all over the world contributed. Industrial spoil in the rest of Britain was removed with the help of state aid following post-Aberfan legislation.
One of the first acts of the Labour Government when it was elected in 1997 was to pay the £150,000 back, but many believe that if inflation and interest rates were taken into account, the figure should have been nearer £1.5m. Locals believe that such a sum of money is needed to keep the specially built community centre going and fund the upkeep of the memorial garden built on the site of the school. A large cemetery overlooking the valley where some graves bear the pictures of the dead children also needs to be tended.
Some, including Gaynor, believe that additional compensation is due to those whose lives were irreversibly affected.
A memorial ceremony on Thursday night at a local church was a difficult time for those attending. Another private service will be held today.
Gaynor has retained her religious faith, but since the disaster her mother has been an atheist, always wondering how a benevolent God could allow such a thing to happen.Reuse content