If it wasn't being slowly exposed in a corruption inquiry in the County Court, many Victorian parents would struggle to believe the evidence about how large sums of money meant for the state's school system have been systemically rorted by two allegedly corrupt officials.

On Tuesday morning, the latest chapter in the tale of this alleged graft was played out. It, too, was almost unbelievable, not only because of the sordid details, but also because of what it says about the culture of largesse and impunity within the top ranks of Victoria's education department.

This latest story involves a "business" trip overseas whose participants - two top and now former public servants - may not have actually conducted any official business at all.

The former acting secretary of the Education Department, Jeff Rosewarne, is at the centre of the scandal.

He approved an around the world, taxpayer-funded business-class trip for his friend and departmental colleague Nino Napoli. Not one to miss out on the action, Mr Rosewarne met Mr Napoli in London before ducking off to Rome for a few days.

Under questioning on Tuesday morning at the Independent Broad Based Anti-Corruption Commission hearing, Mr Rosewarne could not recall the name of any person or educational institution he and Mr Napoli supposedly met over four days in London in October 2009.

The London meetings were used by Mr Napoli to justify his official request for funding for the trip. But neither man filed a report of their trip as required.

After prompting from counsel assisting the IBAC hearing, Ian Hill, QC, Mr Rosewarne also revealed that Mr Napoli most likely had paid for his then wife, Anne Rosewarne, to travel business class with them on the trip.

Mr Napoli is another central figure at the IBAC inquiry into alleged serious corruption within Victoria's Education Department.

Until recently the finance manager of the department, Napoli has been accused of running a fraud ring that delivered potentially millions of dollars to his relatives.

Mr Napoli also picked up the tab for the Rosewarnes' accommodation in Rome.

Evidence presented at IBAC shows Mr Rosewarne was on good terms with some of Mr Napoli's relatives, but he has denied he was ever aware of them being awarded large taxpayer-funded contracts by schools or the department.

In regards to the 2009 trip, Mr Rosewarne explained that he did not have the money to pay for his then wife's airfares and had been in the habit of asking Mr Napoli to pick up such personal bills.

He believed her airfares cost about $8000.

Asked if he himself had paid his wife's airfares, Mr Rosewarne replied: "I indirectly paid for them."

He then detailed how Mr Napoli would regularly fill the breach when his $200,000 plus annual income could not meet his personal expenses, such as family holidays and travel.

Mr Rosewarne said he always repaid Mr Napoli in cash. He also revealed that once, in 2011, he borrowed $5000 from Mr Napoli's motor mechanic cousin Carlo Squillacioti, to pay for a family holiday. Mr Rosewarne also claims to have paid this money back.

IBAC has produced invoices showing several companies owned by Mr Squillacioti receiving large payments from Victorian schools and the department over several years. The allegations being tested by IBAC include whether Mr Squillacioti was being used as a middleman by Mr Napoli and Mr Rosewarne to help the pair launder money stolen from the department.

IBAC has also raised the issue of Mr Rosewarne possibly misleading a government insurer after a departmental car crashed into the garage of his home in 2011.

Mr Hill asked Mr Rosewarne if he had told Mr Napoli on the night of the accident that his unlicensed daughter was actually driving the car at the time of the crash. Mr Rosewarne said he could not recall.

An email from the insurance company showed the claim had listed Mr Rosewarne as the driver of the vehicle. The insurance company said the policy did not cover damage to the driver's home.

Mr Rosewarne was also quizzed by IBAC about why his personal tax returns were done, free of charge, by Napoli over a 10-year period. This line of questioning by IBAC was aimed at exposing the close and allegedly corrupt ties between the two men as they systemically ripped off the Education Department. 

For his part, Mr Napoli stands accused of running a potential $2.5 million fraud ring to benefit his relatives and himself over seven years. The cash came from money meant to go to state schools.

Emails show Mr Rosewarne was involved in contracts being awarded to companies owned by relatives of Mr Napoli, who is a registered tax agent.

Mr Rosewarne has denied any knowledge of Mr Napoli's family being paid large sums by schools and the department during his tenure as a top official, which ended in 2011. But Rosewarne has also been grilled about his own use of public funds.

Ian Hill, QC, on Tuesday morning produced documents showing how Mr Rosewarne spent more than $5000 on two coffee machines at Harvey Norman in 2009 by using a school credit card and bogus invoices prepared by his friend, former Brighton Primary School principal Gordon Pratt.

Mr Rosewarne said Mr Pratt offered to pay for the two machines. One machine was used in his office and another went to his home.

He said he chose not to use his corporate card to avoid others in the department knowing and creating a climate where "everyone would want one".

Mr Pratt was on Monday revealed as a participant in a false invoicing scam orchestrated by Mr Rosewarne in 2008 whereby Brighton Primary School paid $4600 invoice for "decor" to hide the cost of the party.

Mr Rosewarne said the coffee machines were returned to the school at a later date. He could not recall if the school was reimbursed for the cost of the machines.

IBAC also produced emails and invoices showing Mr Rosewarne hid the cost of furniture he claimed was for his home office by having a school provide an invoice to a furniture supply for "printing" services.

Mr Rosewarne admitted the owner of the furniture company was a longstanding friend of his, and also known to Mr Napoli.

The Moonee Ponds West Primary School was initially to have paid for Mr Rosewarne's furniture. But it did not do so after its principal, Tony Hill, left. So the invoice was sent to Chandler Park Primary School, which was led by a friend of Mr Rosewarne, Peter Paul. The school paid the invoice.

Mr Rosewarne admitted that no one in the department knew of or approved his purchase of home furniture until 2013, two years after he left. Mr Hill accused Mr Rosewarne of hiding his spending by "subterfuge".

The hearing continues.