"We have stolen the Picasso from the National Gallery," read the ransom note, addressed to Victoria's then arts minister Race Mathews.

The year was 1986 and the Weeping Woman painting, purchased by the National Gallery of Victoria for some $1.6 million just one year prior, was nowhere to be seen.

But this was no normal theft, declared the thieves, known only as the Australian Cultural Terrorists.

This was a crime of passion — a protest against the "niggardly funding of the fine arts in this hick state and against the clumsy, unimaginative stupidity of the administration and distribution of that funding".

Authorities had seven days to meet the thieves' demands, the letter said, or the painting would be destroyed.

The ransom letter, delivered to Race Mathews, poked fun at him by labelling him "rank". ( Google Archives )

A $1.6m price tag — and no insurance

"We'd be terribly lucky if it [the exhibition of the painting] went without any brouhaha," remarked then director of the National Gallery of Victoria, Patrick McCaughey, in what would become somewhat of a droll prediction.

It was December 1985 — eight months prior to the painting's disappearance — and Mr McCaughey was marking the launch of the gallery's new purchase.

Patrick McCaughey predicted the Weeping Woman would "haunt Melbourne". ( ABC TV )

The Weeping Woman, painted by Picasso in 1937 during the same period as his famed Guernica, and modelled on his mistress Dora Maar — his own "weeping woman" — was the most important 20th century work the gallery had acquired.

But with a $1.6 million price tag, it was not without controversy.

Nor was it insured, with those in power considering the cost of insurance for major works of art "prohibitive".

"This face is going to haunt Melbourne for the next 100 years," Mr McCaughey beamed at the launch.

Indeed, the Weeping Woman would haunt the city — but not in the way he had planned.

The great art heist

It was a crime so simple it was almost inconceivable.

The painting was unscrewed from the wall and carried out of the gallery unnoticed sometime after closing on Saturday August 2, 1986.

The thieves even left a calling card indicating the painting had been removed for routine maintenance, signing it with the initials ACT (Australian Cultural Terrorists).

So preposterous was the heist, it was not reported for three days.

"Confronting the bare wall and the fake label, I was aghast," Mr McCaughey wrote in his book, The Bright Shapes and the True Names.

"I excused myself from the committee meeting and began a search of the gallery, desperately hoping that it was a prank and that the painting had been hidden in the building."

Authorities were at a loss. Could it be an inside job?

After all, the thieves clearly knew their art history — some suspected the heist was an ironic homage to the 1911 theft of the Mona Lisa from the Louvre, in which Picasso himself was a suspect.

Victorian police initially suspected art smugglers were behind the theft. ( Google Archive )

Others, including Mr Mathews, questioned if the vigilante group was but a red herring, a cover for a "more serious criminal operation designed to smuggle the painting out of the state".

Then the ransom letters arrived.

'The smell of kerosene and burning canvas'

The letter was typewritten and the authors hardly minced their words.

Addressed to Mr Mathews via a local newspaper, the letter warned the painting would be destroyed if the Victorian government failed to meet the thieves' demands.

The Victorian government refused to bow to the group's demands. ( Google Archive )

The group stipulated the minister must agree to a 10 per cent increase in funding for the arts, and create an annual art prize — worth $25,000 — named The Picasso Ransom.

"There will be no negotiation," the letter, dated August 5, 1986, said.

"At the end of seven days if our demands have not been met, the painting will be destroyed."

However the letter was met with a swift rebuke from Mr Mathews, who remarked he would not be "budgeting by blackmail".

And so, at least it would seem, they found themselves at a stalemate.

Authorities launched an investigation, but no-one — including the art world — appeared any closer to unearthing the identity of the self-styled Australian Cultural Terrorists.

Then, after another four days of silence, the second letter arrived.

The second ransom letter warned the arts minister would smell "burning canvas" if the thieves' demands were not met. ( ABC News )

"Good luck with your huffing and puffing, Minister, you pompous fathead," read the note addressed to Mr Mathews and dated August 9 — one week after the heist.

"If our demands are not met, you will begin the long process of carrying about you the smell of kerosene and burning canvas."

A third letter containing a burnt match arrived at the minister's office two days later.

"Thank you for your support. Phase two begins shortly," was all it said.

The luggage locker on Spencer Street

With the thieves' seven-day deadline having well and truly passed, authorities' hopes of finding the Weeping Woman were fading.

Subsequent searches of the gallery and sketches of potential suspects seen nearby had failed to yield any signs of the painting, or the Picasso poachers, who had fallen silent since delivering their third letter.

The Weeping Woman was found in locker 227 at the Spencer Street railway station. ( ABC TV )

That was until police and the press received an anonymous phone call almost three weeks after the artwork's disappearance.

Go to Spencer Street railway station, the tipster said, there you will find the Weeping Woman hidden in locker 227.

"The police beckoned me to look inside and there was a brown paper package exactly the dimensions of Picasso's [painting]," Mr McCaughey recalls in his memoir.

"The gallery's chief conservator, who was now on hand, whipped the package into a waiting police car with journalists running after us.

"We were whisked up to the forensic laboratory where the painting was unpacked and Weeping Woman emerged unharmed."

An anonymous phone call led police and the press to the locker. ( ABC TV )

In their final letter, delivered in the days after the find, the Australian Cultural Terrorists would concede they "never looked to have our demands met".

The great Picasso caper had come to an anti-climactic end as the Weeping Woman found her way back on the walls of the National Gallery of Victoria.

Who were the Australian Cultural Terrorists?

Despite exhaustive inquiries — including raids of private galleries and a $50,000 reward — more than three decades later, authorities are no closer to uncovering the true identity of the art vigilantes.

According to police, it is likely the Australian Cultural Terrorists comprised "three and perhaps more" people who were "in the art world or on the fringe of the art world".

A sketch of a woman who police say was sighted near locker 227 with a brown parcel. ( ABC TV )

At least two women were sighted with a parcel near locker 227, they said, while the anonymous phone call was believed to have been placed by a man.

But, pending "any solid evidence rather than innuendo and speculation", the case will remain closed, the major crimes squad declared in 1989.

Mr McCaughey has his own theories about the theft.

In his memoir, he recalls receiving a call from a Melbourne art dealer — just days before the painting was recovered — who said a young artist may have information about the theft.

He visited the artist's studio near the Victoria Market where he discovered photos and newspaper clippings about the theft pinned to the walls.

"I said deliberately, at least twice, that the people who had taken the work could deposit it in a luggage locker at Spencer Street railway station or at Tullamarine airport," Mr McCaughey wrote.

"I always found it notable … that within 48 hours of that visit, with the explicit advice about placing the work in a locker … the painting reappeared.

"Did the Australian Cultural Terrorists hear of this and think we might be getting close?"

At least for now, it would seem, we will never know.