They have been jointly analysing evidence implicating Unaoil in serious corruption - evidence that was uncovered by Fairfax Media and the Huffington Post last year. The evidence is voluminous and compelling. It shows Unaoil paid bribes or engaged in illegal activity to win contracts for major oil industry companies across the globe, including in Algeria, Iraq, Libya, Iran and Kazakhstan.

Top officials, including two former Iraq oil ministers, are among those whom Unaoil or its agents sought to corrupt. Unaoil's graft on behalf of these major companies is compounding inequality in some of the poorest countries in the world.

In the past few months, major US and British companies, including KBR, Petrofac and Rolls Royce, have revealed that they are assisting authorities or have launched internal investigations into their own dealings with Unaoil.

The Iraq government has also launched a major inquiry. The BBC, CNBC, The Guardian and reporters across Europe, the Middle east and Africa have dug up fresh angles on the Unaoil story.

It is a big story. Unaoil's predictable response has been to distract, deny and threaten legal action.

However, it has a major problem. Some Unaoil files explicitly describe paying off government officials, while others reveal money laundering and cartel behaviour.

Unaoil has never answered specific questions about its bribery. We sent it a long list of questions, days before publishing a series of stories in April. Those questions remain unanswered.

As part of our revelations, we wrote about meeting one of our key sources, whom we had codenamed 'Le Figaro' (this person had asked us to place an advertisement in Le Figaro newspaper to establish contact). We had our first dealings with Le Figaro in June 2015 and that person was the catalyst for our corruption expose.

What we have not reported until now is that Le Figaro not only contacted us in June 2015; they also contacted the Australian Federal Police anti-bribery team (because Unaoil had paid bribes on behalf of the offshore arm Australian company Leighton Holdings).

In the event, the source chose to work with us, although they regularly requested we pass information to the police. We relayed Le Figaro's revelations to the AFP in June 2015 and, in the months following, to the US Department of Justice, the FBI, the City of London Police and, in October 2015, the Serious Fraud Office (SFO).

Le Figaro wanted anti-bribery authorities to launch a major investigation into Unaoil. Le Figaro believed a big media expose would help achieve this.

Along the way, new sources came forward to give us additional information. In October and November more of Unaoil's files and emails started arriving. We were told they had been removed from Unaoil's system by the Ahsani family, which owns and runs the company, because they contained damning information about corruption.

We notified authorities that we were receiving this information, and passed the files to the authorities, months before we published our series of expose. We also spoke to sources inside large companies that had employed Unaoil and suspected they were corrupt.

Then, the day after we published our first Unaoil story on March 30, we learned that the SFO had raided Unaoil alongside Monaco authorities. An unnamed Monaco government official described it as "a case of vast corruption with international ramifications".

Perhaps predictably, Unaoil's response has been to launch a distraction campaign.

Six weeks after our revelations, Unaoil's London public relations firm, Tancredi, gave a story to News Corp's The Australian newspaper. Their story revealed Unaoil's claims that it had been the subject of an extortion attempt launched by an unknown person who claimed to be Russian and who, between December 10 and March 25 (after we had received data and given it to the police) threatened to release information to the media or WikiLeaks that exposed Unaoil's corruption, unless he was paid a large sum of money.

Unaoil never raised any extortion plot with our team of reporters prior to, or after, we published our story. Had Unaoil told us it had been extorted, we would have reported it to our readers.

We would have also pointed out that it did not diminish evidence exposing Unaoil's rampant corruption.

Curiously, Unaoil also did not tell police about the extortion attempt. Rather, it chose to pay off the extortionist, saying it did this on the advice of experts.

Our best guess is that someone who had been close to the Ahsanis had fallen out and was trying to play on their fear that the company's bribery may be exposed.

Hard as it tries, Unaoil's public relations campaign can't distract from the issue of its corruption. Rather, it illustrates how the "bribe factory" will do anything to avoid being brought to account. It is an attempt to muddy the waters.

Unaoil's lawyer Rebekah Giles has stated she will launch a defamation action against Fairfax Media. This is no idle threat. Unaoil is worth hundreds of millions of dollars, and could spend years pursuing unwarranted litigation. It may also be that the Ahsanis fear being charged by police and hope that a law suit may bolster their inevitable "trial by media" claims.

But consider this: Unaoil's owners, Ata, Cyrus and Saman Ahsani, are all suspects in a major federal police bribery probe (along with FBI, Department of Justice and SFO inquiries). If they came to Australia, as they would need to in a defamation trial, they would almost certainly be arrested and questioned by federal police over allegations they paid bribes to Iraqi officials on behalf of the offshore arm of Australian company Leighton Holdings.

If the police act on the evidence of Unaoil's corruption, criminal charges will follow.

The defamation tactic appears another attempt to delay, obfuscate and threaten. Perhaps it is a coincidence that it was flagged just days after we sent the company another list of questions, this time asking about evidence revealing Unaoil's possible breach of sanctions on Iran, among other serious misdeeds.

Just like the first set of questions we sent, our latest remains unanswered.

We can assure our readers that defamation actions and media campaigns by wealthy corporate crooks will not stop our reporting.