It was one of the most politically contentious business deals which took place while Ireland was recovering from the financial crash.

At the time, many big companies were in difficulty and banks were trying to recoup as much money as they could.

A firm beneficially controlled by businessman Denis O'Brien, called Millington, bought a business services company group, Siteserv, in 2012.

These days, Siteserv is called Actavo, and its vans and hoardings are a common site as it installs telecoms infrastructure, and works on civil engineering projects, in Ireland and abroad.

But, in 2012, Siteserv was under significant financial pressure and owed IBRC, the former Anglo Irish Bank, €150m.

When Siteserv was sold for €45m in 2012, the bank wrote off €119m of the €150m it was owed.

As IBRC was State-owned, the loan was effectively owed to the taxpayer.

One of the biggest issues raised following the deal was a claim that IBRC could have recouped more money by selling Siteserv to another bidder.

A fund called Anchorage claimed to have offered a higher price.

Siteserv was sold for €45m in 2012 (Pic: Rolling News)

One source close to the deal at the time told me that there were too many conditions attached to rival offers, and that the bid from Denis O'Brien was the only concrete deal on the table.

However, the fact that a rival bidder raised questions about how much money the State could recoup sparked a flurry of political claims that the taxpayer could have got a better deal.

To complicate matters further, the bank agreed that the deal could include a €5m payment to the shareholders in Siteserv.

This is unusual, because normally, if a bank is writing off money, the shareholders would be completely wiped out.

The argument put forward when the deal proceeded was that, if the shareholders objected, they could have held up the deal at a time when Siteserv was in financial difficulty, and time was running short to save the company.

A third unusual aspect of the transaction was that law firm Arthur Cox was acting for Siteserv, but also acted for Denis O'Brien during the purchase.

Arthur Cox did put in place a Chinese wall to manage any perceived conflict of interest.

Nonetheless, the multiple issues surrounding the transaction created significant political unease.

The co-leader of the Social Democrats Catherine Murphy raised questions in the Dáil about the transaction.

Under massive political pressure, the then Fine Gael-led government appointed Judge Brian Cregan to lead a Commission of Investigation into the matter.

While his probe was to look into a wide range of write-offs by IBRC, the first on the list was the Sitesev deal.

Seven years later, he has published his report into that transaction.

Along the way, many questions have been asked about the length of time it has taken to conclude the inquiry and the expense.

Two years ago, Government had estimated the cost of the investigation would be €30m.

Aontú TD Peadar Toibin said the final figure could reach €70m.

But like everything about the Siteserv deal, even the inquiry into it has been controversial.