Like so many of you, I've watched the royal commission into robodebt with competing emotions of frustration, anger, sorrow and admiration (for the brave victims, whistleblowers, families and honest public servants) and utter disbelief that this could happen in Australia.

Across nine weeks of hearings, Commissioner Catherine Holmes AC SC, in a no-nonsense forensic but compassionate manner, oversaw a series of hearings with more than 100 witnesses.

Among those to take the stand were former Liberal prime ministers and portfolio ministers responsible for the unlawful scheme, a range of senior bureaucrats, affected workers, and people who were either victims of the scheme or whose loved ones were victims and are no longer here to speak for themselves.

Robodebt changed lives and, for mothers like Jenny Miller and Kath Madgwick, who grieve children who ended their lives after receiving a notice for a debt they didn't owe, they believe extracted the ultimate price.

How could this happen — and continue to happen? That is the question.

Robodebts were calculated by Centrelink applying averaged Australian Tax Office PAYG income data across either part or all of the fortnights in which the recipient received payments.

Those averaged amounts were treated as the recipient's actual earnings in the relevant debt period. In a way that ignored what people actually earned.

Federal Court Justice Bernard Murphy said: “The proceeding has exposed a shameful chapter in the administration of the Commonwealth social security system and a massive failure of public administration.”

The consequences of this finding was far reaching.

It meant that under the former government's robodebt scheme, which ran from July 2015 until it was halted in November 2019, 416,000 Australians had been issued with unlawful debts.

The government had to repay at least 381,000 people $751 million and wipe all debts — worth $1.76bn — that were raised using the unlawful method of “income averaging”.

This was a cynical exercise by a Coalition government hell-bent on boasting a Budget surplus, consequences be damned.

They did not care that the most vulnerable in our society would be the ones paying — not only in financial terms but with their mental and physical health.

One of the last witnesses at the royal commission, former Centrelink social worker Taren Preston, summed up the approach from senior executives as “so sad, too bad” when she raised concerns about the distress the scheme was causing Centrelink customers and staff.

Take a minute to think about that. Ms Preston was telling her bosses that vulnerable people were coming to her feeling hopeless, expressing suicidal thoughts and they just shrugged it off.

I can't get my head around it. Australians are not heartless. But for a period there, under successive Liberal prime ministers, our government was.

Alan Tudge, former minister for human services, would have us believe the details of robodebt were not his concern. Tudge resigned a couple of months back.

In his final speech to Parliament there was not one word of remorse for the pain he had caused. Not one. He even had the gall to say that his “passion has always been in social policy”.

When former prime minister and social services minister Scott Morrison got into the witness box, he tried answering the questions he wished he'd been asked. Commissioner Holmes and Counsel Assisting Justin Greggery KC pressed him for a straight answer.

After four years as prime minister, watching him fudge answers and “not accept he premise of the question”, nobody was surprised when his words were devoid of substance. No less infuriating though.

And then we had former government services minister Stuart Robert, who would have us believe that he was also a victim because he had to toe the Cabinet solidarity line.

Robert told us that he didn't want to emphatically defend the scheme a number of times in the media, but he did.

He even said that in 92 per cent of cases, the debts raised were correct.

This is despite admitting under oath that he had a “massive personal misgiving” about the legality of the robodebt scheme.

Victims of robodebt were desperate for someone to listen. The former Liberal government was desperate to remain wilfully ignorant. They had Budget-themed coffee mugs emblazoned with “Back in Black” to sell, after all.

When they finally shut the scheme down, it was for purely political purposes, not to stem the human misery they had unleashed against vulnerable Australians.

And yet, in the mire of meanness these were beacons of light.

People like Colleen Taylor, a frontline Centrelink worker who was clear as she recounted her first-hand knowledge of the unethical robodebt scheme.

Of how she took the evidence all the way to Department of Human Services secretary, Kathryn Campbell, but nothing changed. Colleen Taylor was a study in courage, integrity and empathy against a backdrop of obfuscation and indifference.

But I will be forever grateful to all the witnesses in the royal commission who shared personal stories of how robodebt affected their lives.

I've recently used question times to tell the stories of victims because the extent of the human tragedy that is robodebt is only just being understood.

Members of the Opposition squirm in their seats as I talk about mothers who couldn't feed their children because money had vanished from their accounts; honest people made to feel like criminals; young people who ended up in hospital for months after attempting suicide.

To the Coalition front and backbenchers who were part of this dark stain on Australia's soul, I say that the few minutes of discomfort you feel is nothing compared to the lifetime of trauma you have caused.