(CNN) Yami Lester was 12 years old when the black mist came to Walatinna.

Early on the morning of October 15, 1953, Lester heard a "big bang" in the distance. This was followed by a dark, ominous-looking cloud which drifted low over the ground like a slow-moving dust storm, bringing with it an unpleasant smell.

A tiny speck in the vast South Australian outback, the area around Walatinna was regarded as "depressingly inhospitable to Europeans" by early colonizers, few of whom settled there. But Indigenous people had a long history in the region, including Lester's tribe.

As the dark cloud settled over the Walatinna camp, the tribal elders attempted to ward it off, thinking it was a malevolent spirit. In many ways they were right.

As those exposed to it later told investigators, the black mist caused their eyes to sting and their skin to break out in rashes. Others vomited and suffered from diarrhea.

It took almost three decades until the cause of the mist was acknowledged as the Totem I nuclear bomb test, as Indigenous people had been claiming for years.

That test was one of a number conducted in the 1950s and '60s, not by the Australian government, but by its former colonial master, the UK. Today, 65 years after the Totem I test, the effects are still being felt in South Australia and beyond.

British bomb

Australia was not the UK's first choice of nuclear testing site. British scientists had been intimately involved in the Manhattan Project during World War II, and fully expected to be able to follow the US in testing their own nuclear weapon on American soil.

However, after it emerged Soviet spies had infiltrated the US atomic program, Washington passed the McMahon Act , which strictly limited the sharing of nuclear information with other countries and sent London looking for new locations to conduct its first test.

Menzies, and wide open spaces in which to carry out the detonations themselves. "Ultimately, they settled on Australia, which had many benefits," said Elizabeth Tynan, author of " Atomic Thunder: The Maralinga story ," a book about the tests. These includes a sympathetic, compliant government under the recently elected Anglophile Prime Minister RobertMenzies, and wide open spaces in which to carry out the detonations themselves.

In September 1950, British leader Clement Attlee sent Menzies a secret message asking whether his government "would be prepared in principle to agree that the first United Kingdom atomic weapon should be tested in Australian territory."

According to a later Australian Royal Commission investigation , Menzies "immediately agreed to the proposal," without consulting any of his cabinet colleagues or the Australian parliament. Indeed, until weeks before the first test was carried out, only three government ministers knew about it.

Menzies' enthusiasm for the British bomb "wasn't all sycophantism, it wasn't all sucking up to his colonial masters," said Tynan, though this was definitely a factor. The Australian leader also saw in the atomic age an advantage for his country, which was one of the few to have large stocks of uranium, a previously largely unwanted material.

The UK's first atomic bomb was detonated in the waters off the Montebello Islands, a small archipelago in north western Australia, in the early hours of October 3, 1952, officially making London the third member of the nuclear club, after the US and the Soviet Union.

Emu Field

While the Montebello Islands were used for the first test, British planners were never totally happy with the location, and even before the bomb was set off they began looking for a site on the Australian mainland where they could be granted greater secrecy and autonomy.

They settled on a location in the Great Victoria Desert, about 480 kilometers (300 miles) from the nearest town, Woomera, which they named Emu Field.

Plans were soon set in motion for a second test, and on October 15, 1953, the first of the Totem devices was detonated.

Unlike the Montebello test, which went off largely as planned, the 9.1 kiloton Totem I sent a cloud of debris and smoke some 15,000 feet (4,500 meters) into the air, spreading fallout far higher and farther than originally expected.

The Royal Commission later found the test was carried out in inappropriate wind conditions and without proper consideration for people living nearby, examples of the often staggering lack of care taken by British officials overseeing the nuclear program, who frequently ignored or did not bother to seek out vital information about the potential effects of their tests on the host country.

A man in protective clothing at Maralinga with a camera also protected by a plastic cover. National Archives of Australia, A6457, P214

Black mist

The most devastating effects were suffered by two groups: Australian and British soldiers working on the tests themselves, and the Indigenous populations local to Emu Field and the later testing site of Maralinga.

While some concern was paid to their safety during the tests, it was often cursory at best. A single "native patrol officer" given the thankless task of having to try and inform Indigenous residents of the potential dangers had a 100,000 square kilometer (38,610 square mile) region to cover.

Nor did the British much seem to care. One prominent member of the testing team, Sir Ernest Titterton, later said that if Indigenous people had a problem with the government, they should vote it out, ignoring that Indigenous Australians did not have full political rights until 1967.

Another senior official, in a letter to his superiors, complained that W. B. MacDougall, the man with the dubious task of trying to protect the local Indigenous populations, was "placing the affairs of a handful of natives above those of the British Commonwealth of Nations."

"The harm done to the Aboriginal people is one of the most shameful aspects (of the tests)," Tynan said. "Nowhere in the British records is there a sign of even the slightest concern for the Aboriginal people."

This lack of concern is likely what led to the situation at Walatinna. Around 40 people were in the camp when the Totem I blast sent clouds of radiated material miles into the sky.

"It rumbled, the ground shook, it was frightening," Lalli Lennon told investigators. Some time later, a large black cloud passed low over the settlement. Her husband Stan described it as "sort of hazy, like a fog or something." Lalli and her children developed fevers, headaches, vomiting and diarrhea, and two of them suffered rashes and sore eyes from the smoke.

But just as they had paid little attention to the wellbeing of Indigenous people prior to the test, the British and Australian authorities did not concern themselves with such matters afterwards.

This was reflected by and large by Australian public opinion, which Tynan said was initially "quite jubilant" about the tests, and remained broadly supportive until the 1970s and '80s, when a host of revelations about the British nuclear program exposed its lackluster safety procedures — even by the standards of the time — and the disdain of those overseeing it for Australian democratic oversight.

Panorama of the Maralinga front gate, the southern boundary the Woomera nuclear testing site, on May 05, 2011 in Australia.

Maralinga mess

This shift began when an Australian defense ministry report was leaked to the press , warning that large amounts of plutonium left at Maralinga could potentially be a target of terrorists.

This ran contrary to a 1968 report prepared by British official Noah Pearce which assured the Australian government the plutonium had been properly buried and did not present a significant risk.

Indeed, that year the Australians agreed to release the UK from nearly all "liabilities and responsibilities" regarding the tests, in the belief the British had "completed decontamination and debris clearance ... to the satisfaction of the Australian government."

When Canberra finally carried out its own survey of the site, scientists were shocked by what they found.

"They still thought the Pearce Report was accurate until their geiger counter went crazy," said Tynan, who has interviewed several of the inspectors. "They weren't wearing protective gear (and) were kicking plutonium soaked rocks with their boots."

The Royal Commission report said later that there were between "25,000 and 50,000 plutonium- contaminated fragments in the (Maralinga) area, although the number might need to be doubled if missed and buried fragments were included." Emu Field and the Montebello Islands were also found to be more dangerous than expected.

"In addition to British scientific and military personnel, thousands of Australians were exposed to radiation produced by the tests," according to a report by the Australian Institute of Criminology. "These included not only those involved in supporting the British testing program, but also Aboriginal people living downwind of the test sites, and other Australians more distant who came into contact with airborne radioactivity."

A prohibited area sign seen near the Maralinga nuclear test site in 1974.

Final hearing

The Royal Commission hearings marked the end to any lingering approval of the tests among the Australian public, exposing fully the ongoing harm done to the local environment, Indigenous people, and the soldiers who worked on the tests.

While many disorders are difficult to link directly to the nuclear tests, veterans of the program have complained of numerous cancers, autoimmune diseases, and other ailments — including among their children — which they put down to their lack of protective clothing and other precautions at the time.

Last year, the Australian government expanded medical benefits for members of the nuclear testing program, but most are now in their late 80s and one told the ABC the move was "too bloody late."

The harm done to Indigenous people has also been recognized in the decades since the Royal Commission, including by the black mist -- which a British official once said investigating would be a "complete waste of money and time."

In 1993, the British agreed to pay the Australian government and the traditional owners of the Maralinga lands around 46 million AUD ($30 million). The Australian authorities also paid Indigenous Maralinga communities a settlement of 13.5 million AUD ($9 million).

"Everyone became friends again after that," said Tynan, adding that the issue, which had dominated Australian media and public attention for years, slowly slipped away, becoming a "great Australian secret."

Today, she said she often meets young Australians who are unaware of the tests, and even many people who were alive at the time of the Royal Commission who only have a hazy idea of the issues.

"It was one of those things that, because it was not really written into the history books ... just dropped off the radar," she said, even as veterans and Indigenous people affected by the tests continue to suffer health repercussions and shortened lifespans because of their exposure to radiation.

Yami Lester died on July 21, 2017. He was remembered in parliament by then Prime Minister Malcolm Turnbull as a "man of wonderful intelligence and insight, as an elder of great standing and as a champion of Aboriginal rights and dignity."

"He will be revered for rising from personal tragedy to serve his community and to lead his people to ensure that they were recognized and their wrongs addressed," Turnbull added.

But as Tynan and others have pointed out, those wrongs have not been fully addressed. Health problems stemming from the tests continue for those still living, and while the veracity of Lester and other victims' stories has been acknowledged, what exactly happened to them remains unclear, the details of the nuclear test still kept top secret.

"To this day we don't know what Totem I did, those records are still classified by the British," Tynan said. "It remains one of the great mysteries."