It's stayed with her

This Is The Queen's Biggest Regret Of Her Reign

Over her many decades as monarch, Queen Elizabeth II has occasionally attracted criticism and been at the centre of controversy. But one of the Queen's decisions in the 1960s plunged the Royal Family deeply into a crisis — which is said to be her biggest regret.

October 21, 1966, began as an ordinary day in Aberfan, Wales. But it ended in disaster when a 34-meter-high spoil broke loose and slid down Mount Merthyr, burying homes and an elementary school in the mining village. The result: 144 people died, 116 of them children.

Across Britain, there was anger at how the accident could have occurred and great sorrow over the loss of so many young lives. The royals were also devastated by the tragic news.

Queen Elizabeth visited Aberfan — but after 8 days had passed

Queen Elizabeth II sent a message of condolence to Aberfan, but she did not travel to Wales until eight days after the disaster. Prince Philip, on the other hand, visited a day after the slide. Many people were incensed that the Queen had not initially come to Wales in person, causing something of a scandal for the royals.

But, on Oct. 29, the Queen herself arrived in Aberfan and visited the relatives of the victims. Her former private secretary Sir William Heseltine told the documentary Elizabeth: Our Queen it was one of the few times that the monarch cried in public.

Queen Elizabeth II.

"Aberfan affected the Queen very deeply, I think, when she went there," Heseltine said. "I think she felt in hindsight that she might have gone there a little earlier. It was a sort of lesson for us that you need to show sympathy and to be there on the spot, which I think people craved from her."

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The Queen regrets her Aberfan decision

According to biographer Sally Bedell Smith, the Queen's decision was one with practical intentions. Smith said the Queen told her that she feared people would be tending to her during the visit rather than continuing to search for survivors at the site of the accident.

To this day, this decision is one of the few things the Queen regrets in her nearly seven-decade reign. The incident was also revisited in The Crown season 3, showing the Queen's decision making and personal struggles with the event.

Queen Elizabeth and Jeff Edwards, who survived the Aberfan disaster at age 8.

But, nearly 40 years after disaster, survivor Jeff Edwards told South Wales Echo that the Queen "came when she could and nobody would condemn her for not coming earlier, especially as everything was such a mess." Since 1966, the Queen has visited the Welsh town more often than any other member of the Royal Family.