Mr Glennon sent an $18,000 invoice in March, after developing a range of marketing strategies and website content for Mr Constable's new company, Carlton Ross and Associates.

Perhaps predictably, Mr Glennon has not been paid and is now considering launching bankruptcy proceedings against his client.

"We're obviously kicking ourselves now, but we just assumed he was an honourable man. And yes, when we were made aware of his book title we became a lot more dubious about his bona fides," Mr Glennon said.

But Mr Glennon was unaware that Mr Constable had an extensive history of defaulting on debts dating back almost 40 years.

Mr Constable, 65, who has also used the alias Douglas Duckett, had already been declared bankrupt on three occasions since 1988, leaving a string of angry creditors in his wake.

He has been linked to almost 50 shelf-companies since 1985 and was convicted of obtaining financial advantage by deception in 1997. He regularly changes business premises, with at least one landlord claiming to be owed six months' unpaid rent.

In 2013, Mr Constable was refused a liquor license for a Geelong cafe by the Victorian Commission for Gambling and Liquor Regulation due to "convictions for dishonesty and traffic offences, outstanding warrants and failure to disclose full particulars of his prior convictions."

Despite his tainted corporate history, the Australian Securities and Investment Commission allowed Mr Constable to establish Carlton Ross and Associates Pty Ltd in 2013, which he now uses to advise those facing financial hardship.

"With over 50 years business experience, we've assisted clients to see a complete picture of their business and financial circumstances and we provide simple, smart solutions to keep people moving forward," Mr Constable claims on his LinkedIn account.

When contacted by Fairfax Media, Mr Constable insisted he would settle the debt with Mr Glennon and denied having any other significant creditors.

"I looked them both in the eye and told them they'd get paid ... As a show of good faith I offered $1000 a month until my funds come through," Mr Constable said.

But he warned Mr Glennon against taking bankruptcy action.

"This is a company debt, not a Doug Constable debt ... If he goes down the legal path, he may get paid or he may not get paid. If he works with me, given the circumstances, he will get paid," Mr Constable said.

But Mr Glennon has a different version of events. In March, he paid $180 for Mr Constable to attend a charity lunch for the Windermere Foundation and organised that he sat next to Carlton legend Stephen Kernahan at the event.

"He [Constable] told me at that lunch that our invoice had been paid, only to be told a few days later that he'd sacked his bookkeeper and that's why it wasn't paid. Because he's like a Walter Mitty character, you simply don't know what to believe," Mr Glennon said.