The Royal Commission into Trade Union Governance and Corruption opened in early 2014, hearing from more than 500 witnesses and sitting across the country.

Look back at 10 key moments from the almost two-year inquiry.

Bill Shorten

The public spotlight was thrown onto Bill Shorten's time at the helm of the Australian Worker's Union (AWU), both as Victorian secretary (1998-2006) and later, as national secretary (2001-2007).

He faced heavy questioning over failing to declare contributions from the labour hire company Unibilt to his 2007 election campaign.

The Opposition leader faced heavy questioning during over failing to declare a $43,000 donation. ( AAP: Lukas Coch )

During proceedings, it was revealed he had only declared the $43,000 donation just two days before his appearance at the royal commission.

The commission also looked at the union's relationship with one of the country's biggest construction firms Thiess John Holland.

It examined invoices for the firm's advertisements that the commission claimed were never published.

Mr Shorten denied he would agree to employers paying for services not received.

Mr Shorten was also accused of manufacturing other deals, such as the arrangement with cleaning company Cleanevent, that would be to the detriment of workers' conditions, a claim which Mr Shorten strenuously denied.

On the second day of his evidence, Justice Heydon warned Mr Shorten that his credibility as a witness was at risk and that it was in his interest "to curb these, to some extent, extraneous answers".

Julia Gillard

After years of enduring allegations she had operational knowledge of a secret AWU slush fund run by her former boyfriend, Bruce Wilson and AWU organiser Ralph Blewitt, Julia Gillard was cleared of wrongdoing by the royal commission.

The interim report found "that Julia Gillard did not commit any crime and was not aware of any criminality". ( AAP: Alan Porritt, file photo )

The interim report found "Julia Gillard did not commit any crime and was not aware of any criminality".

Her long-anticipated appearance revealed little in the way of new facts, although the former prime minister conceded she "would do the whole thing differently" if she could.

Commissioner Heydon did not believe suggestions Ms Gillard knew renovations on her house were funded by union money.

Instead he accepted Ms Gillard's testimony that she "took steps to satisfy myself that looking at the amount of work that has been performed on my home, that I had paid for it all".

One of the criticisms of Ms Gillard in the interim report was a lapse in "professional judgement" and some sloppy administration when dealing with the establishment of the AWU fund.

The commission also found "her powerful instinct for self-preservation" made it difficult to judge her credibility as a witness and she demonstrated "occasional evasiveness, or non-responsiveness, or irritability".

Kathy Jackson and the HSU

When the woman who blew the whistle on former Health Services Union boss Michael Williamson and former Labor MP Craig Thomson made her appearance at the commission, it was standing room only in the public gallery.

It was alleged Kathy Jackson misused hundreds of thousands of dollars in union funds to buy luxury goods, fund overseas trips and holidays and to pay off personal credit cards.

She was also asked to account for a $250,000 payout from the Peter MacCullum cancer hospital that was allegedly supposed to be paid to members.

But her controversial appearance became notorious after she objected to being questioned by HSU counsel and former lover Mark Irving whom she labelled her "charity shag".

Variously described as "heroic" and "a brave, decent woman" by Tony Abbott, Ms Jackson is now a declared bankrupt and was found to have misused HSU funds and ordered to pay $1.4 million.

CFMEU

The royal commission opened the lid on a hidden culture of violence and a coercive internal culture within Australia's Construction, Forestry, Mining and Energy Union.

Over a long period, the union has been embroiled in allegations of death threats and workplace assaults.

Several states subsequently established police taskforces to deal with myriad accusations against CFMEU officials that arose in the royal commission.

The first individual charged under this regime was Queensland CFMEU official Justin Steele, who now stands accused of assaulting a female developer on a Brisbane construction site.

The commission also heard evidence CFMEU NSW organiser Darren Greenfield made death threats against former union official Brian Fitzgerald.

In another case, Victorian CFMEU official John Perkovic was banned from Australian work sites for 18 months for "a serious and ugly confrontation" with a federal government investigator at an Adelaide construction site.

ACT hearings and the CFMEU

The hearings in Canberra during July turned the spotlight back on allegations of union corruption at a grass roots level.

The most high-profile case was that of former CFMEU official Fihi Kivalu, who was dramatically arrested less than an hour after completing his evidence to the commission.

Kivalu was committed to stand trial on blackmail charges.

There were another two arrests on the sidelines of the Canberra hearings — former Canberra Raiders NRL star and CFMEU official John Lomax and Tuungafasi Manase (an acquaintance of Kivalu).

Allegations of blackmail were formally dropped against Mr Lomax, while Manase is accused of giving misleading evidence to the commission.

These were the firsts arrests to happen during commission hearings.

George Alex & CFMEU

George Alex, a well-known Sydney underworld figure, has been described as the lynchpin connecting Australia's construction industry to Sydney's criminal underbelly.

George Alex stood accused of paying CFMEU officials $2,500 in weekly kickbacks to curry favour with his construction companies. ( AAP: Dan Himbrechts )

He has been photographed with Comanchero bikie enforcers as well as Islamic State terrorists (who Alex claims did boxing training at his house).

His business partner and standover man Joe Antoun was shot dead in 2013.

Mr Alex has connections to construction companies spanning the east coast of Australia, including Barangaroo on Sydney's harbour foreshore.

The royal commission summonsed Alex to determine whether the CFMEU had received "secret commissions or other benefits" from his construction companies.

He stood accused of paying CFMEU officials $2,500 in weekly kickbacks to curry favour with his construction companies.

The commission also investigated the so-called "phoenixing" of companies associated with Alex, whereby he stood accused of evading taxes by intentionally allowing his companies to go bankrupt and transferring their assets to other entities under his or his associates' control.

Mr Alex denied these allegations. In particular, Alex was quizzed about his relationships with Brian Parker, who has since stepped down from his position as CFMEU NSW state secretary, and other union officials.

Industry 2020

The Victorian AWU slush fund was set up in 2008 at the direction of then secretary Cesar Melham. Mr Melham, who is now a Labor MP for Western Victoria, was also Mr Shorten's successor.

It was alleged the fund's purpose was to bankroll Mr Melham's union re-election campaigns.

It was also revealed the fund helped Mr Melham's Health Services Union allies who received $27,000.

Among the high-profile events staged by Industry 2020 was a 2008 fundraiser Julia Gillard attended. It raised $254,000.

Mr Melham conceded during the hearings he "should have never handed cash to anyone".

Mr Melham also answered questions he allegedly traded $2 million of workers' penalty rates for payments to the union.

After his appearance, Mr Melham resigned as Victorian Upper House whip.

TWU

The Transport Workers Union's (TWU) "fighting funds" and other monies were examined by the commission but it was in Western Australia that it was revealed TWU officials spent $300,000 on prestige cars.

Hearings also heard evidence Toll Holdings had paid $350,000 into a "training fund" to allegedly settle an industrial dispute.

But it was an examination of its super fund arrangements that drew the most attention.

The commission heard evidence the union received $200,000 in directors' fees, $500,000 in salaries for super "liaison officers" and $100,000 in sponsorship and special payments.

Former Toll employees gave evidence they were forced to join the TWU's super funds.

SDA/MUA

The commission heard claims the Maritime Union of Australia (MUA) extracted more than $1 million from companies involved in offshore gas projects for industrial peace.

Emails from company executives paying money to the MUA though the payments sounded "a little too much like a bribe".

Chris Ketter was the first sitting MP to front the trade union royal commission in August 2014. ( Australian Labor Party )

Counsel assisting described one of the union's associated funds as little more than "a bank account of the MUA" used to cover day-to-day expenses.

National secretary Paddy Crumlin rejected the suggestion the union had been involved in anything unlawful and accused the Government of waging a "jihad" against workers rights.

Queensland Labor senator Chris Ketter was the first sitting MP to front the trade union royal commission in August 2014.

Under the microscope was his conduct as state secretary and treasurer of the shop, Distributive and Allied Employees Association (SDA), known as the Shoppies.

The commission heard evidence Mr Ketter sacked one of his organisers who nominated to challenge him in a union election.

A claim Mr Ketter dismissed as "coincidence".

As with other unions, the commission focused on the SDA's $400,000 fighting fund.

It was claimed members had no choice but to contribute to the fund and that it was understood they would have no stake in how the money was spent.

One witness said the culture within the union was anti-gay and anti-abortion and that "dossiers" on delegates and organisers were compiled to ensure they remained on message.

"There were members out there who would have loved to have been delegates, but couldn't because of their sexual orientation."

Dyson Heydon

After it was revealed Dyson Heydon had accepted an invitation to speak at a Liberal Party fundraiser and deliver the Sir Garfeild Barwick address, Labor, the Greens and the ACTU called on the Government to shut down the royal commission.

While the ACTU threatened to take the commissioner to the High Court, historical links between Justice Heydon and Tony Abbott were revealed, including his presence on a selection panel that awarded the former prime minister a prestigious Rhodes Scholarship in the 1980s.

On August 21, Justice Heydon heard the ACTU's case that he should disqualify himself on the grounds of bias.

Union counsel said the commission's final report must have credibility but that observers "would be left in a state of doubt sufficient to think that you might not be able to bring an impartial mind to these highly sensitive matters".

Justice Heydon spent more than a week assessing disqualification submissions from the ACTU, AWU and CFMEU for him to recuse himself as commissioner.

But on August 31, he ruled he would stay on in the role, arguing it was not the case a "fair-minded, lay observer" would conclude he would be incapable of bringing an "impartial mind" to the work of the commission.