On Saturday, there will be a march from Australia House in London to Parliament Square, the centre of British democracy. People will carry pictures of the Australian publisher and journalist Julian Assange who, on 24 February, faces a court that will decide whether or not he is to be extradited to the United States and a living death.

I know Australia House well. As an Australian myself, I used to go there in my early days in London to read the newspapers from home. Opened by King George V over a century ago, its vastness of marble and stone, chandeliers and solemn portraits, imported from Australia when Australian soldiers were dying in the slaughter of the First World War, have ensured its landmark as an imperial pile of monumental servility.

As one of the oldest "diplomatic missions" in the United Kingdom, this relic of empire provides a pleasurable sinecure for Antipodean politicians: a "mate" rewarded or a troublemaker exiled.

Known as High Commissioner, the equivalent of an ambassador, the current beneficiary is George Brandis, who as Attorney General tried to water down Australia's Race Discrimination Act and approved raids on whistleblowers who had revealed the truth about Australia's illegal spying on East Timor during negotiations for the carve-up of that impoverished country's oil and gas.

This led to the prosecution of whistleblowers Bernard Collaery and "Witness K", on bogus charges. Like Julian Assange, they are to be silenced in a Kafkaesque trial and put away.

Australia House is the ideal starting point for Saturday's march.

"I confess," wrote Lord Curzon, Viceroy of India, in 1898, "that countries are pieces on a chessboard upon which is being played out a great game for the domination of the world."

We Australians have been in the service of the Great Game for a very long time. Having devastated our Indigenous people in an invasion and a war of attrition that continues to this day, we have spilt blood for our imperial masters in China, Africa, Russia, the Middle East, Europe and Asia. No imperial adventure against those with whom we have no quarrel has escaped our dedication.

Deception has been a feature. When Prime Minister Robert Menzies sent Australian soldiers to Vietnam in the 1960s, he described them as a training team, requested by a beleaguered government in Saigon. It was a lie. A senior official of the Department of External Affairs wrote secretly that "although we have stressed the fact publicly that our assistance was given in response to an invitation by the government of South Vietnam", the order came from Washington.

Two versions. The lie for us, the truth for them. As many as four million people died in the Vietnam war.

When Indonesia invaded East Timor in 1975, the Australian Ambassador, Richard Woolcott, secretly urged the government in Canberra to "act in a way which would be designed to minimise the public impact in Australia and show private understanding to Indonesia." In other words, to lie. He alluded to the beckoning spoils of oil and gas in the Timor Sea which, boasted Foreign Minister Gareth Evans, were worth "zillions".

In the genocide that followed, at least 200,000 East Timorese died. Australia recognised, almost alone, the legitimacy of the occupation.

When Prime Minister John Howard sent Australian special forces to invade Iraq with America and Britain in 2003, he - like George W. Bush and Tony Blair - lied that Saddam Hussein had weapons of mass destruction. More than a million people died in Iraq.

WikiLeaks was not the first to call out the pattern of criminal lying in democracies that remain every bit as rapacious as in Lord Curzon's day. The achievement of the remarkable publishing organisation founded by Julian Assange has been to provide the proof.

WikiLeaks has informed us how illegal wars are fabricated, how governments are overthrown and violence is used in our name, how we are spied upon through our phones and screens. The true lies of presidents, ambassadors, political candidates, generals, proxies, political fraudsters have been exposed. One by one, these would-be emperors have realised they have no clothes.

It has been an unprecedented public service; above all, it is authentic journalism, whose value can be judged by the degree of apoplexy of the corrupt and their apologists.

For example, in 2016, WikiLeaks published the leaked emails of Hillary Clinton's campaign manager John Podesta, which revealed a direct connection between Clinton, the foundation she shares with her husband and the funding of organised jihadism in the Middle East - terrorism.

One email disclosed that Islamic State (ISIS) was bankrolled by the governments of Saudi Arabia and Qatar, from which Clinton accepted huge "donations". Moreover, as US Secretary of State, she approved the world's biggest ever arms sale to her Saudi benefactors, worth more than $80 billion. Thanks to her, US arms sales to the world - for use in stricken countries like Yemen - doubled.

Revealed by WikiLeaks and published in The New York Times, the Podesta emails triggered a vituperative campaign against editor-in-chief Julian Assange, bereft of evidence. He was an "agent of Russia working to elect Trump"; the nonsensical "Russiagate" followed. That WikiLeaks had also published more than 800,000 frequently damning documents from Russia was ignored.

On an Australian Broadcasting Corporation programme, Four Corners, in 2017, Clinton was interviewed by Sarah Ferguson, who began: "No one could fail to be moved by the pain on your face at [the moment of Donald Trump's inauguration] ... Do you remember how visceral it was for you?"

Having established Clinton's visceral suffering, the fawning Ferguson described "Russia's role" and the "damage done personally to you" by Julian Assange.

Clinton replied, "He [Assange] is very clearly a tool of Russian intelligence. And he has done their bidding."

Ferguson said to Clinton, "Lots of people, including in Australia, think that Assange is a martyr of free speech and freedom of information. How would you describe him?"

Again, Clinton was allowed to defame Assange - a "nihilist" in the service of "dictators" - while Ferguson assured her interviewee she was "the icon of your generation".

There was no mention of a leaked document, revealed by WikiLeaks, called Libya Tick Tock, prepared for Hillary Clinton, which described her as the central figure driving the destruction of the Libyan state in 2011. This resulted in 40,000 deaths, the arrival of ISIS in North Africa and the European refugee and migrant crisis.

For me, this episode of Clinton's interview – and there are many others – vividly illustrates the division between false and true journalism. On 24 February, when Julian Assange steps into Woolwich Crown Court, true journalism will be the only crime on trial.

I am sometimes asked why I have championed Assange. For one thing, I like and I admire him. He is a friend with astonishing courage; and he has a finely honed, wicked sense of humour. He is the diametric opposite of the character invented then assassinated by his enemies.

As a reporter in places of upheaval all over the world, I have learned to compare the evidence I have witnessed with the words and actions of those with power. In this way, it is possible to get a sense of how our world is controlled and divided and manipulated, how language and debate are distorted to produce the propaganda of false consciousness.

When we speak about dictatorships, we call this brainwashing: the conquest of minds. It is a truth we rarely apply to our own societies, regardless of the trail of blood that leads back to us and which never dries.

WikiLeaks has exposed this. That is why Assange is in a maximum security prison in London facing concocted political charges in America, and why he has shamed so many of those paid to keep the record straight. Watch these journalists now look for cover as it dawns on them that the American fascists who have come for Assange may come for them, not least those on the Guardian who collaborated with WikiLeaks and won prizes and secured lucrative book and Hollywood deals based on his work, before turning on him.

In 2011, David Leigh, the Guardian's "investigations editor", told journalism students at City University in London that Assange was "quite deranged". When a puzzled student asked why, Leigh replied, "Because he doesn't understand the parameters of conventional journalism".

But it's precisely because he did understand that the "parameters" of the media often shielded vested and political interests and had nothing to do with transparency that the idea of WikiLeaks was so appealing to many people, especially the young, rightly cynical about the so-called "mainstream".

Leigh mocked the very idea that, once extradited, Assange would end up "wearing an orange jumpsuit". These were things, he said, "that he and his lawyer are saying in order to feed his paranoia".

The current US charges against Assange centre on the Afghan Logs and Iraq Logs, which the Guardian published and Leigh worked on, and on the Collateral Murder video showing an American helicopter crew gunning down civilians and celebrating the crime. For this journalism, Assange faces 17 charges of "espionage" which carry prison sentences totalling 175 years.

Whether or not his prison uniform will be an "orange jumpsuit", US court files seen by Assange's lawyers reveal that, once extradited, Assange will be subject to Special Administrative Measures, known as SAMS. A 2017 report by Yale University Law School and the Center for Constitutional Rights described SAMS as "the darkest corner of the US federal prison system" combining "the brutality and isolation of maximum security units with additional restrictions that deny individuals almost any connection to the human world ... The net effect is to shield this form of torture from any real public scrutiny."

That Assange has been right all along, and getting him to Sweden was a fraud to cover an American plan to "render" him, is finally becoming clear to many who swallowed the incessant scuttlebutt of character assassination. "I speak fluent Swedish and was able to read all the original documents," Nils Melzer, the United Nations Rapporteur on Torture, said recently, "I could hardly believe my eyes. According to the testimony of the woman in question, a rape had never taken place at all. And not only that: the woman's testimony was later changed by the Stockholm Police without her involvement in order to somehow make it sound like a possible rape. I have all the documents in my possession, the emails, the text messages."

Keir Starmer is currently running for election as leader of the Labour Party in Britain. Between 2008 and 2013, he was Director of Public Prosecutions and responsible for the Crown Prosecution Service. According to Freedom of Information searches by the Italian journalist Stefania Maurizi, Sweden tried to drop the Assange case in 2011, but a CPS official in London told the Swedish prosecutor not to treat it as "just another extradition".

In 2012, she received an email from the CPS: "Don't you dare get cold feet!!!" Other CPS emails were either deleted or redacted. Why? Keir Starmer needs to say why.

At the forefront of Saturday's march will be John Shipton, Julian's father, whose indefatigable support for his son is the antithesis of the collusion and cruelty of the governments of Australia, our homeland.

The roll call of shame begins with Julia Gillard, the Australian Labor prime minister who, in 2010, wanted to criminalise WikiLeaks, arrest Assange and cancel his passport – until the Australian Federal Police pointed out that no law allowed this and that Assange had committed no crime.

While falsely claiming to give him consular assistance in London, it was the Gillard government's shocking abandonment of its citizen that led to Ecuador granting political asylum to Assange in its London embassy.

In a subsequent speech before the US Congress, Gillard, a favourite of the US embassy in Canberra, broke records for sycophancy (according to the website Honest History) as she declared, over and again, the fidelity of America's "mates Down Under".

Today, while Assange waits in his cell, Gillard travels the world, promoting herself as a feminist concerned about "human rights", often in tandem with that other right-on feminist Hillary Clinton.

The truth is that Australia could have rescued Julian Assange and can still rescue him.

In 2010, I arranged to meet a prominent Liberal (Conservative) Member of Parliament, Malcolm Turnbull. As a young barrister in the 1980s, Turnbull had successfully fought the British Government's attempts to prevent the publication of the book, Spycatcher, whose author Peter Wright, a spy, had exposed Britain's "deep state".

We talked about his famous victory for free speech and publishing and I described the miscarriage of justice awaiting Assange – the fraud of his arrest in Sweden and its connection with an American indictment that tore up the US Constitution and the rule of international law.

Turnbull appeared to show genuine interest and an aide took extensive notes. I asked him to deliver a letter to the Australian government from Gareth Peirce, the renowned British human rights lawyer who represents Assange.

In the letter, Peirce wrote, "Given the extent of the public discussion, frequently on the basis of entirely false assumptions... it is very hard to attempt to preserve for [Julian Assange] any presumption of innocence. Mr. Assange has now hanging over him not one but two Damocles swords, of potential extradition to two different jurisdictions in turn for two different alleged crimes, neither of which are crimes in his own country, and that his personal safety has become at risk in circumstances that are highly politically charged."

Turnbull promised to deliver the letter, follow it through and let me know. I subsequently wrote to him several times, waited and heard nothing.

In 2018, John Shipton wrote a deeply moving letter to the then prime minister of Australia asking him to exercise the diplomatic power at his government's disposal and bring Julian home. He wrote that he feared that if Julian was not rescued, there would be a tragedy and his son would die in prison. He received no reply. The prime minister was Malcolm Turnbull.

Last year, when the current prime minister, Scott Morrison, a former public relations man, was asked about Assange, he replied in his customary way, "He should face the music!"

When Saturday's march reaches the Houses of Parliament, said to be "the Mother of Parliaments", Morrison and Gillard and Turnbull and all those who have betrayed Julian Assange should be called out; history and decency will not forget them or those who remain silent now.

And if there is any sense of justice left in the land of Magna Carta, the travesty that is the case against this heroic Australian must be thrown out. Or beware, all of us.

18 February 2020

- John Pilger is an Australian-British journalist and filmmaker based in London.

www.johpilger.com

@johnpilger

The march on Saturday, 22 February begins at Australia House in Aldwych, London WC2B 4LA, at 12.30pm: assemble at 11.30pm