The revelation in March 2019 that a former gangland barrister called Nicola Gobbo was also a police informer was a legal scandal like no other – one that threatened the foundations of the state's criminal justice system and some of Victoria Police's most celebrated convictions.

The scandal, unfolding largely in secret and shrouded by suppression orders, took almost a decade to play out until the Director of Public Prosecutions finally decided Ms Gobbo's former clients had a right to know that she might have informed on them, breaching her duties as their lawyer.

The police fought for years in the courts to try to keep her name from public disclosure. They took the case all the way to the High Court, which found in December 2018 that Victoria Police’s conduct in using her as a confidential informer was "reprehensible" and had corrupted prosecutions.

It left Victorian Premier Daniel Andrews with no choice but to call a royal commission into the police's handling of Ms Gobbo and other informers.

Thousands of news stories and millions of dollars later, two convicted criminals released and many others launching appeals, now the royal commission has handed down its final report.

So what was the Nicola Gobbo scandal all about? What have we learned since she was named? And what will happen next?

Who is Nicola Gobbo and what did she do?

The 48-year-old niece of the former Victorian governor Sir James Gobbo, was one of the youngest women ever admitted to the bar in 1998. She made a name for herself during the gangland era in the early 2000s by representing a rogue's gallery of Melbourne's underworld, including murdered gangster Carl Williams and drug kingpin Tony Mokbel.

She was also a police informer, and under the registration number 3838, she gave police information about her criminal associates, many who had been or were clients.

What's wrong with a lawyer being a police informer?

The problem is when a lawyer gives police information about their own clients.

Conversations between lawyers and the people they represent are protected by what's called legal professional privilege, which keeps communication between lawyers and clients confidential. This is supposed to enable clients to talk without fear the information will be used against them, and lawyers to provide legal advice knowing the full picture.

There are exceptions to this, including if the communication is for the purposes of the client committing a crime. But in Ms Gobbo's case, she was giving police information about her own clients and in some cases, representing them in court while simultaneously informing on them. She was completely conflicted.

This conflict rigs the system and perverts the concept of a fair trial, which is a cornerstone of the justice system, because Ms Gobbo wasn't just failing to be independent from the prosecution when she was acting as a defence lawyer, she was an agent of police.

The High Court in its 2018 judgment (when it was deciding whether Ms Gobbo's name should be revealed to her clients) said as a result, prosecutions were "corrupted in a manner which debased fundamental premises of the criminal justice system".

How did Nicola Gobbo become an informer?

Ms Gobbo's dealings with police stretch back to her Melbourne University days. She was first registered as a police informer in 1995 when she was still a law student.

At the time, she had been feeding police information about a boyfriend after their Carlton house was raided for drugs two years earlier (Ms Gobbo got away with a good behaviour bond).

Ms Gobbo was registered a second time in 1999, the year after she became a barrister, because she was supplying information about another lawyer who she claimed was laundering money.

But it's her third registration from 2005 to 2010, when she became Informer 3838, that's at the heart of this controversy.

The reasons she became an informer are mixed. Lawyers for the commission said she demonstrated a willingness to provide information to police, even if it was contrary to her interests or those of her clients. Though the force footed some of Gobbo's expenses along the way (including tickets to see pop star Pink in concert), it wasn't about the money.

She had also suffered a stroke the year before, at the age of 32, and said she was under stress from her notorious and violent clients.

"I'm here because I've had enough ... and I don't know the way out," she told her police handlers the first time she met them (the meeting was secretly recorded). "I'm nearly 33, what have I done with my life? I've had a stroke, I get up at six o'clock, go to work by seven, spend all day working, very rarely do I go anywhere or do anything … for what?"

Ms Gobbo herself told the royal commission she was also driven by a need to be wanted, and to belong.

"Looking back I wanted to belong, I wanted to be the, the, um, the holder of every bit of information about every drug trafficker up and down the supply chain," she told the inquiry.

"It was mostly my, pathetic as it sounds, my inability to say no and my, my need to be, I guess to be wanted or to be valued or feel valued."

From the police side of things, she had information that they wanted, particularly on Mokbel, and had become so close to her criminal client that they suspected she was involved in his syndicate.

And in the context of the gangland wars (a notorious spate of murders and shootings between gangs over the drug trade in Melbourne), police had confronted a so-called "wall of silence" from the players who would not give information on each other. They could not resist the information.

"I have a duty of care to her and that is to make sure she doesn't get hurt," one of her main handlers told the royal commission, "but I have a role as a policeman to see if she has access to information that could be useful to ... stop the gangland killings."

What are the key findings of the royal commission?

In the four-volume, 1000 page report, the key recommendation by the commissioner, Margaret McMurdo was the establishment of a special investigator who was independent from Victoria Police and the Director of Public Prosecutions, to consider whether criminal charges should be brought against current and former Victoria Police.

Ms McMurdo found the convictions or findings of guilt of 1011 people may have been affected by Victoria Police's use of Ms Gobbo as a human source, and she was scathing of Ms Gobbo, saying her "duplicitous and improper conduct spanned a period of more than 15 years".

Some members of Victoria Police had fallen short of their legal, moral and ethical duties, and as a result, "they corrupted the criminal justice system," Ms McMurdo found. The police generally, including senior officers who knew, "tolerated bending the rules to help solve serious crime". They also failed until far too late to get legal advice about Ms Gobbo's use as an informer, and found the "compelling" reason for that was "that Victoria Police did not want to be told they could not use Ms Gobbo in the ways they intended".

Of other potential Gobbos – members of the legal and allied professions being used as informers – Ms McMurdo found no wrongdoing, but noted that it did not have access to 11 human source files because police invoked a public interest immunity argument. More work was required to establish if there were further problems in those cases.

Why have police fought so hard to keep elements of this scandal secret?

The scandal is embarrassing, but by making it public, it also threatens several high-profile convictions that police worked hard to ensure. But police say they wanted to keep Ms Gobbo's double dealings a secret because they were scared she'd be killed.

"That risk has been spoken of so often that it is easy to forget what it really meant," Victoria Police lawyers submitted to the commission.

"It meant that if Ms Gobbo's role became known then it was highly likely she would be murdered."

Until a suppression order was lifted last year, her identity had been hidden behind her registration number - Informer 3838 - and the pseudonym of EF that she was given in court.

The force were also worried the exposure of Ms Gobbo would not only endanger her life and those of her two young children, but create a "chilling effect" on people coming forward to give information to police, undermining confidence in the police's ability to keep their informers' identities a secret.

How did this come to light?

It was a controversial former detective by the name of Paul Dale that set the ball rolling. Mr Dale was charged, though never convicted, over the 2004 double murder of Terence and Christine Hodson. The investigation was the most significant police corruption case in the state's history (Mr Dale said he had nothing to do with it).

When that case collapsed, Mr Dale faced fresh criminal charges of lying to the Australian Crime Commission (which he was acquitted of). Ms Gobbo was the key witness against him. Mr Dale requested documents from Victoria Police through the court process to find out more about her relationship with police.

Victoria Police didn't want to hand over documents, fearing it would reveal the extent of Ms Gobbo's relationship with police, so they sought legal advice for the first time. The 2011 legal advice warned convictions were at risk because of the use of the lawyer as an informer.

In response, former chief commissioner Graham Ashton commissioned a review, called the Comrie Review, which then led to a secret Independent Broad-based Anti-corruption Commission inquiry.

Newspaper The Herald Sun also began writing about Ms Gobbo (referring to her as Lawyer X). As the pressure increased, the Office of Public Prosecutions and Victoria Police went to court to fight disclosing her identity to her clients. That's where the High Court came in, finally ruling that disclosure to her former clients could occur. That led to the suppression order on her identity to be lifted and the royal commission established.

Has anything like this happened before?

There have been isolated cases of lawyers dobbing on their clients in the United States (you can read about that here), but there has been no known case in global history on the scale of Ms Gobbo, academics have previously told The Age.

"Nothing to this extreme, that we know of, has happened anywhere in the world," Melbourne University law professor Jeremy Gans said.

Supreme Court justice Timony Ginnane also described the conduct as "unprecedented".

What will this mean for Gobbo's former clients? Will they all be let out of jail?

The royal commission said the convictions or findings of guilt of 1011 people may have been affected by Ms Gobbo's involvement, including Mokbel's.

Two convictions have been quashed already and several appeals are before the court at the moment. The first conviction to fall was Faruk Orman's. After more than a decade behind bars, the Court of Appeal set his conviction for the 2002 murder of gangster Victor Peirce aside.

The decision was based on the Director of Public Prosecutions' concession that a substantial miscarriage of justice occurred when Ms Gobbo acted as Orman's lawyer and also encouraged a gangland turncoat to become a witness against her own client.

The court decided Orman didn't have to undergo a retrial as he had served so much time already.

The second conviction to go was Zlate Cvetanovski's, who had been behind bars for 11 years for drug trafficking.

The Court of Appeal quashed his conviction (and as with Orman, decided he should not face a retrial) for a couple of reasons. The first was that Victoria Police failed to disclose Ms Gobbo's informer role, and the second was police didn't disclose the secret payments they made to the key witness against Cvetanovski.

Under the law, any compensation provided to a witness must be disclosed in criminal proceedings because they are considered "inducements" that can affect a witness' credibility. The failure to disclose the payments meant Cvetanovski couldn't properly test the evidence against him.

"The principles governing disclosure are fundamental to the integrity of criminal trials and to the maintenance of public confidence in the administration of justice," president of the Court of Appeal, Justice Chris Maxwell, said.

Mr Orman is now suing the police for millions and its expected Mr Cvetanovski will do the same.

As well as Mokbel's appeal, several men convicted over what's known as the tomato tins ecstasy bust are also appealing, notably Frank Madafferi and Rob Karam. Karam gave Ms Gobbo shipping documents that identified a container of tomato tins travelling from Italy to Melbourne that had 15 million pills hidden inside. Ms Gobbo copied the information and gave it to police. She then went on to represent a few of the men arrested over the bust.

Who has been implicated?

Aside from Ms Gobbo, Ms McMurdo was critical of some of the force’s most senior and decorated officers - including former chief commissioners Simon Overland and Graham Ashton, former gangland taskforce detective Stuart Bateson and taskforce bosses Jim O’Brien and Gavan Ryan.

She accused Mr Ashton, who retired this year, of failing in his duty by not acting to stop prosecutions contaminated by Ms Gobbo, including the prosecution of Mokbel, in 2011.

Ms McMurdo said Mr Ashton, when he was chief, could and should have conveyed a clear public message about the improper and unacceptable conduct by Victoria Police when the scandal came out.

In response, Mr Ashton's lawyers said: "Any attempt to put a sinister overlay on Mr Ashton's conduct is the product of speculation and mischaracterising the facts."

As for Mr Overland, Ms McMurdo said he should have identified the grave risks involved in registering a criminal defence barrister as a human source.

She said Mr Overland likely did not seek legal advice about her use because it would limit the information he hoped to obtain from Ms Gobbo to help solve the gangland wars.

Ms McMurdo said there was an “unacceptable willingness throughout the organisation to tolerate bending the rules to help solve serious crime".

Questions have also been raised about who in the legal sector knew and did nothing about it either. Ms Gobbo's lawyers told the royal commission there was material suggesting two current Supreme Court judges and former heads of public prosecutions at a state and federal level knew, at the very least, Ms Gobbo was acting in conflict.

"The only lawyer who was scrutinised and criticised was Ms Gobbo," they said.

Will anyone be charged?

Ms McMurdo made no recommendations for criminal charges, saying that would normally be up to the prosecuting authorities. But the Director of Public Prosecutions (DPP) said it would not prosecute, and passed the buck to the state's criminal investigation agencies, Victoria Police and the Independent Broad-based Anti-corruption Commission.

IBAC said it didn't have the jurisdiction, and Victoria Police took no action when IBAC referred its 2015 findings to then chief commissioner Ashton.

With no clear path out of the mess, Ms McMurdo recommended the establishment of a brand new investigative body, saying in her report's "key recommendation" that the government should appoint a special investigator with full powers to examine whether Ms Gobbo committed any criminal offences connected with her conduct as a police source.

According to Doug Drummond QC, who was appointed a special prosecutor following Queensland's Fitzgerald royal commission, such a model was required so the prosecutor was free of political interference.

What lasting reforms will there be?

Victoria Police has overhauled the way informers are managed, disbanding the team that handled Ms Gobbo and putting in place a new human source management unit. But the commission has suggested more changes in its 111 recommendations, which have all been accepted by the government.

The reforms make for dry reading, but they're integral to the way the justice system works, for example, thecommission called for independent oversight over police sources in the form of a public interest monitor, and more powers and resources for the state's watchdog the Independent Broad-based Anti-corruption Commission (IBAC) to investigate police.

The recommendations also revealed that police have created a disclosure officer position (which exists in the UK) and a committee, which involves independent organisations, whose job would be to oversee what documents are disclosed or kept secret during a court case.

The commission has also called for a new laws to involve prosecutors in decisions about confidentiality claims, also known as public interest immunity claims, in court proceedings. These claims make secret information on the basis it may put an investigation or an informer at risk, but the claims have been over-used, with police conceding information would be redacted without distinction.

This kind of thing is relevant to what happened with Ms Gobbo as her identity was often hidden in court proceedings (on at least one occasion she was allowed to look through the police evidence on her client to make sure her identity wasn't disclosed to them) so there was no independent oversight on what was going on with her use.

What will happen to Nicola Gobbo?

As talked about before, we don't know whether Ms Gobbo will face criminal charges either. We also don't know where Ms Gobbo is, as she's in hiding, so the practicalities of charging her would be difficult.

She may well sue Victoria Police again too.

In her first lawsuit in 2010 she asked for $20 million in compensation and received a $2.88 million settlement after her double life imploded. Ms Gobbo was turned from informer to witness (meaning she'd have to publicly give evidence in court) in the failed case against Paul Dale for the murders of Hodson, who was also a police informer, and his wife Christine.

The Age reported earlier this year that Ms Gobbo has already briefed a legal team to launch fresh civil action.

How much has all this cost?

The bill for the royal commission was sitting at $39.5 million, which is on top of the $1.5 million a month that former police chief Ashton estimated was costing Victoria Police for staff and legal fees for the inquiry.

Ms Gobbo's legal fees alone are more than $2 million, based on a billing pattern in Freedom of Information documents, with the Andrews government agreeing to cover her costs in negotiations last year to secure her participation in the royal commission.

This doesn't take into account the millions that was spent fighting to keep her identity a secret in the lead-up to the commission, nor the expected pay-outs to her affected clients.

What are people saying about it?

“Victoria Police were guilty of reprehensible conduct in knowingly encouraging [the lawyer] to do as she did … As a result, the prosecution of each convicted person was corrupted in a manner which debased fundamental premises of the criminal justice system.” High Court of Australia

“The Commission's findings are serious and significant and individuals and organisations must be held accountable.” Attorney-General Jill Hennessy.

"I would like to make clear today Victoria Police’s absolute acknowledgement that the management of Nicola Gobbo as a human source and the manner in which the information she provided was used, was a profound failure by our organisation that must not, and will not, ever be repeated." Chief Commissioner Shane Patton.

"So, what is the legacy of the Purana Taskforce? They tore the integrity out of policing. This arrogant corruption may have achieved a handful of convictions, two of which have been overturned with potentially many to follow, but it also discredited an entire police force and tore the system apart. The system was supposed to be fair and they made sure it wasn’t. They took the justice out of the justice system and in doing so destroyed the trust between the police and defence upon which that system depends. That is the legacy of the Purana taskforce." Ruth Parker, lawyer who for the two men to have their convictions quashed.

"The integrity of the Victorian justice system has been shredded because of the shortcuts and rules broken that took place during this shocking and tawdry period in Melbourne’s history," Edward O'Donohue, shadow attorney-general in Victoria.