At least not until the man stepped close, twitched his jacket to suggest he was carrying a gun and issued an unforgettable threat to the senior Westpac banker: "I know you have three children – you will do what I say."

The threat was aimed at coercing him to use his personal bank account to facilitate illegal payments for a multimillion-dollar international criminal conspiracy, Mr Knight says.

The alleged conspiracy was run by well-connected Malaysian businessmen who are accused of using Melbourne property purchases at inflated prices to shift millions of dollars of their government's investment funds into their own personal accounts.

Mr Knight says he played his role, paying out tens of thousands of dollars from his account to a middle man. But he only did this because he feared for his family. He later pleaded guilty to fraud offences, avoiding a criminal conviction and receiving community service as a punishment.

But after reading Fairfax Media's June expose of how the Malaysian money-making scheme worked, he realised he had been part of something much bigger: an alleged plot that involved $80 million of Melbourne city properties and kickbacks worth millions of dollars.

It's a scheme that has prompted criminal investigations in two countries and highlighted Treasurer Joe Hockey's concern of illegal international funds flooding Australia's property market.

"I read the [Fairfax] article and I thought, 'Finally I could put it all together'," Mr Knight said.

He first twigged something was wrong with Westpac's well-heeled Malaysian government clients when they introduced a British Virgin Island company into their application for a $22.5-million loan, he told Fairfax Media.

Mr Knight was Westpac's man overseeing the financing of large property developments, but he was familiar with offshore tax haven vehicles, having run an international investment firm before joining the bank in 2011.

Why, he wondered, would a Malaysian government agency – the borrower was a national wealth fund called MARA –  want to deal via a notorious, secretive, offshore tax haven?

Then he was puzzled to discover that the property the Malaysians were buying – a student-accommodation apartment complex in Caulfield, Melbourne, called Dudley House – was significantly overvalued. It was worth around $17 million, but these men were happy to pay $22.5 million.

So he checked the sale prices of several Melbourne CBD properties, including multimillion-dollar office towers in Exhibition Street and Queen Street, which the Malaysian buyers had bought with loans from other major Australian banks for a total of about $80 million.

A property valuer with inside knowledge confided in Mr Knight that the purchase prices of these properties had been "ridiculous".

He said he confronted the Malaysians, telling them they were "clearly paying too much", but they brushed off his concerns. He immediately suspected the buyers were "absolutely corrupt".

"I knew the vendors are taking a super profit and sharing those spoils with the officials," he said.

Mr Knight said he thrived on striking deals and making money for shareholders, so he didn't report his concerns to Australian authorities. (Nor, it seems, did any of the other major banks dealing with the same group). Instead, he had agreed to finance the Caulfield deal at a lending ratio that protected Westpac's interests.

It was within hours of striking that deal on 5 March 2013 that, he claims, he was confronted by a man of Asian appearance outside his Brighton home.

Mr Knight alleged the man threatened his family before instructing the banker to move into his own account the $50,000 the Malaysian officials had just paid to secure its Westpac loan. The man told him to then withdraw the funds in cash and pay him. Mr Knight speculates the man must have been working with the Malaysians as a local fixer.

The transactions were clearly illegal, but Mr Knight made them anyway. "I've spent my whole life dealing in tens of millions of dollars. If you think I'm going to put my family at risk for 50 grand, you are kidding yourself," he said.

On March 6, a day after he claims he was threatened, Mr Knight shifted Malaysian government funds into his personal account in a transaction he would repeat several times. Banking records show that Mr Knight withdrew large amounts of cash - he says he also handed these over to the man.

Mr Knight's lawyer later told a court that Mr Knight "wishes he had gone to police… but the fact is he was in fear of his safety and his family's safety".

It's hard to ignore how Mr Knight's story provides him with a convenient defence for his actions – and his story is not without holes. Victorian police say they found no evidence he was threatened.

"If I am going to pinch money, I am hardly going to move it to the same Westpac account my Westpac salary goes into," Mr Knight said.

In September 2013, during an unrelated audit, Westpac discovered the transfers and called the Victoria Police. The bank says it cannot comment on the case, except to say it had robust anti-money laundering procedures.

The bank sacked Mr Knight, who was then charged with obtaining property by deception.

Last year, a preliminary hearing in the Melbourne Magistrates' Court heard how Mr Knight had shifted into his own account a total of $75,000 linked to the property purchase. Magistrate John Doherty appeared cautiously open to Mr Knight's claim that he had been coerced into moving cash.

"All of us in this courtroom can understand about threats made to your family, particularly you children and your wife," he said. "And that happens from time to time to judicial officers as well. I get that, I really get that."

The magistrate told Mr Knight that if his story was accepted by a court, the case against him would collapse. But he also warned that the alternative could be grim –  if his story wasn't believed, he could be jailed.

Then in June, the Fairfax Media report hit. It showed that, from the $22.5-million property purchase Knight had been involved in, $4.5 million had been skimmed off and returned to senior Malaysian officials.

Our exposé prompted Malaysia's Prime Minister, Najib Razak, to announce a full investigation and Australian Federal Police to raid a house in Melbourne and travel to Malaysia to collect more evidence.

However, at the time Fairfax was not aware how one of Australia's leading banks had facilitated the corrupt transaction. Nor did it have evidence that other Australian banks might have also helped the Malaysian buyers pay deliberately inflated prices on three other multimillion-dollar Melbourne properties.

Then Mr Knight rang to tell his story. He says he had long ago told Westpac and the Victoria Police his story of coercion and about the Malaysians' alleged corruption and kickbacks. It appears neither the bank nor police passed on this information to federal authorities.

"Westpac was just worried about covering their arse – as soon as something goes wrong it is arse-covering mode," Mr Knight said.

Police did not start their investigation until Fairfax Media approached them in late 2014. By then, the former Westpac executive's case had already come before court, where he was told by a magistrate that if he pleaded guilty to moving the funds into his account, he would most likely would escape a criminal conviction and instead perform community service.

Knight took the deal and within a few weeks was working at the Salvation Army. "It was excellent, the people there were just great," he said. "I was sorting, pricing and dealing with customers."

Meanwhile, the federal police are now hot on the trail of Westpac's Malaysian government borrowers and their Australian partners over allegations of bribery, money laundering and tax evasion.

The investigation is ongoing.