As the shotgun-wielding bandit clad in black clothing and a crash helmet burst into the train, a teenage girl instinctively moved for her camera.

She mistakenly thought it was a live performance.

But a motion of the gun made the girl and her friends realise it was actually an armed robbery – a crime that remains unsolved and still fascinates rail enthusiasts half a century on.

The three 16-year-old schoolfriends on holiday had no idea what riches the goods train was carrying as they stepped aboard that morning.

“We were just on a day out,” says Jo Brown, speaking publicly about the robbery for the first time in 50 years.

“We’d heard it was beautiful at Kuranda and thought: ‘That’s where we’ll go’.”

It was a characteristically warm, sticky Far North Queensland morning on December 6, 1973 when the 1800 class rail motor pulled out of Cairns Station carrying about 15 passengers and more than $7,300 in cash pay packets to be hand-delivered to railway maintenance workers.

It was the equivalent of almost $80,000 in today’s money.

Two men well aware of the bonanza on board had hatched what would prove the perfect plan to get their hands on it.

The sudden ambush

In the misty heights of the Kuranda Range, as the train emerged on a right-hand bend from a tunnel into a deep cutting, the driver was forced to bring the rail motor to a halt.

Rail guard Clive Abdy had spotted rocks on the track and went into the driver’s compartment to make sure he’d seen them too.

“As soon as he stopped, I hopped out and went ahead to clear the rocks but there was the big one there that I couldn’t move,” Mr Abdy, now 79, recalls.

“I just didn’t know what to think, or what the caper was.”

Then, he saw the two men.

One went to the back of the train to attach another chain to the track, while the other man boarded the carriage with a gun in his hand.

“It was very quick,” Ms Brown says.

“The train had stopped and in a matter of moments, there was a person in all black, I think it was black motorcycle leathers, with a full-faced black helmet and a sawn-off shotgun in the carriage.

“One of my friends said: ‘Oh I think this must be a show they’re putting on for us’, as if we were important people.

“But we soon realised that wasn’t the case.

“We complied pretty quickly after that.”

Still out on the tracks and down to the ground, Mr Abdy feared the worst.

“When I heard the first shot and saw the pay packets tumble out, I thought they had shot the pay escort,” he says.

‘We huddled on the floor’

Rail historian Antony Roth, who remembers reading about the robbery as an 11-year-old, says it was “like something out of the old West in America”.

It happened on one of the most remote parts of the track, he said, where “you would not expect to be finding anyone”.

The wages had been stored in two boxes, one containing $6,255.29 and the other holding $1,075.67, according to a news report in the Cairns Post the following day.

Several shots were fired during the brief heist, one of which blasted a hole in the luggage compartment of the carriage, but no one was hurt.

“We were in seats facing each other, so we huddled down on the floor and, no, we didn’t move,” Jo Brown says.

Both bandits disappeared down the same drain from which they had emerged, and are believed to have used trail bikes hidden in the rainforest to get away.

Jo Brown remembers staying on the train “for a long time”.

“Somehow, we must’ve got the message that we needed to just not get up when we heard them go,” she says.

“We heard motorbikes go.”

The train wasn’t equipped with two-way radio, so the driver, Ron Barter, had to trek about 3km along the track to Stoney Creek station to raise the alarm using the railways’ internal telephone system.

It gave the bandits head starts of about an hour and a half in their escape.

“I saw these two chaps with the pay boxes jump down into an open drain on the ocean side of the rail and take off,” the late Mr Barter told local paper The Cairns Post that day.

“They didn’t speak to me at all. They spoke to the pay escort who was riding back in the passenger compartment near the driver’s cabin.”

Investigations hit a dead-end

Roadblocks were placed on major routes around Cairns and police combed through the rainforest around Kuranda, but they could not track down the pair.

Officers grilled rail workers in the days that followed to no avail.

The chief of the Cairns criminal investigation bureau at the time, Detective Senior Sergeant James Joseph Bidner, told reporters the robbery had been well-planned.

“They knew what to do, how to do it, and when to do it,” he told reporters in December 7, 1973.

One man detectives questioned was Mr Abdy, but he was never charged.

He says police discovered he had requested time off work before the robbery, telling his employer he was planning to go overseas.

They were running a theory the rail guard wanted to steal the cash for a “bonanza holiday” but he says he’d only been planning a trip to Townsville.

“As far as I’m aware, nothing ever happened [with the case] because they had their mind made up that I was the mastermind behind it, and that’s as far as it went.

“In hindsight, I reckon it was an inside job because there would’ve been oodles of people in Cairns alone that knew this [payroll] operation went on every fortnight.”

Jo Brown says she and her friends – who were only on that train because they’d missed the earlier tourist train by minutes – left their names with the rail ticket office in Cairns but investigators never got in touch.

“In hindsight, I think that is really odd,” she says.

“Maybe they interviewed other people on the train and had what information they needed? I have no idea.”

Queensland Police Service were unable to provide an update on the status of the investigation.

Nobody has ever been charged.

“I don’t think anybody will ever be caught, and I don’t think anybody will ever own up and say: ‘Yeah I done the job’,” Mr Abdy says.