IT was a doomsday cult with more than 60,000 members worldwide, led by a charismatic guru and backed by scientists striving to end the world in one almighty nuclear apocalypse.

But Friday’s execution of Aum Shinrikyo mastermind Shoko Asahara brings to a close WA’s secret role as a testing ground for the first weapon of mass destruction ever to be deployed by terrorists.

And now the 404,000 hectare Banjawarn station, 180km north-east of Laverton where Aum Shinrikyo first tested their WMD, is once again on the market, but this time more level-headed buyers are expected.

Today’s price is $2.5 million but in April 1993, Shinrikyo—a twisted, dangerous mix of religious, anti-government zealots with more than a $1 billion in assets—secretly bought the station for just $400,000.

Forming front companies Clarity Investments and Maha Posya Australia Ltd after Banjawarn’s then owner refused a cash offer, cult leaders began importing transformers, generators, static converters, coaxial cabling, various protective equipment and batteries over the next six months.

Camera Icon A file picture of Shoko Asahara, leader of the Aum Shinrikyo cult that carried out a deadly sarin attack on Tokyo's subway in 1995. Credit: AFP / JIJI PRESS

The companies sought and were granted mining and exploration leases, believing they would stop prospectors or any other unauthorised people coming onto the vast property.

Documents before a 1995 US Senate inquiry examining how the cult slipped under the radar of intelligence agencies revealed it also engaged a West Australian geologist in a bid to begin mining uranium ore from the property.

Then in September 1993, the group dramatically expanded, with six four-wheel drive vehicles and a chartered aircraft carrying Shoko Asahara and 24 of his disciples—five of them girls under 15—arriving at the property.

According to a Federal Police report, they brought with them chemicals and mining equipment, ditch diggers, picks, generators, shovels and, tellingly, gas masks and respirators.

Hardly surprisingly, Customs had earlier found four litres of concentrated hydrochloric acid in containers marked as hand soap, ammonium chloride, sodium sulphate, perchloric acid and ammonium water.

One of them, Seichi Endo, a biochemist and the Aum’s Minister of Health and Welfare, was charged, along with another acolyte, with carrying dangerous goods on an aircraft.

They said they were ignorant of local laws, planning on doing some gold mining, pleaded guilty and were fined $1,750.

Camera Icon This September, 1998, photo shows a facility of Aum Shinrikyo doomsday cult led by its guru Shoko Asahara in Kamikucishiki, Japan. The cult made sarin, a deadly nerve agent, in the facility. Credit: AP

Once back on the land, Endo oversaw the construction of a laboratory on Banjawarn, and filled it with cutting-edge digital equipment, evaporators, beakers, bunsen burners, a rock crushing machine and generators.

While it was never proved that the sect actually carried out explosions at the station, some pastoralists reported loud bangs in the desert night.

A local Indigenous woman, Phyllis Thomas, would later tell police that she saw at least four men dressed in full “space suits” near a twin-prop aircraft, with the rest of them in the plane.

By October 1994, the group had left Banjawarn and had already carried out a gas attack in June in Matsumoto, Japan. It was their attempt to assassinate several judges who were presiding over criminal charges against Aum.

The gas, which investigators later proved had been refined and tested at Banjawarn, was released from a refrigeration truck. Eight people died and over 500 were badly affected.

Then a few months later, Aum Shinrikyo released its own version of sarin gas into the Tokyo subway, killing 13 and injuring another 1000 commuters.

When the new owner took over the Banjawarn lease in 1995, police found a gas mask and a range of chemicals such as nitric acid, ferric chloride, ammonia solution, hydrochloric acid, chloroform, potassium and dichromate.

Documents discovered at the site also revealed that the group was very interested in understanding the process of how to extract uranium.

Camera Icon Aum Shinrikyo cult leader Shoko Asahara and Tomomasa Nakagawa, Seiichi Endo, Masami Tsuchiya, Yoshihiro Inoue, Tomomitsu Nimi, and Kiyohide Hayakawa were executed Friday for a series of deadly crimes including a sarin gas attack on the Tokyo subway that killed 13 people in 1995. Credit: AP

Police also found 29 dead sheep in various state of decay. Further testing would reveal that their wool had traces of chemicals that directly linked it to the Tokyo subway attack.

On Friday, Asahara and six of his accomplices, including the head scientist Endo, were hanged by Japanese authorities for their role in the subway attack.

Another six members of the cult, now a designated terrorist organisation throughout Europe, Canada, the United States and Russia, remain on death row.