Covering the public sessions of the Smithwick Tribunal as a journalist was like taking a tour of some of the murkiest waters of the Troubles.
Disturbing allegations emerged regularly, such as Garda interference with the crime scene where the Narrow Water bombers detonated two devices which killed 18 soldiers.
The tribunal was also told that an RUC intelligence document named a Garda officer it claimed was passing information to the IRA.
Reporters heard of the disappearance of records from Dundalk Garda Station and claims that Garda Assistant Commissioner Eugene Crowley ignored concerns voiced by a senior Garda officer about an IRA mole in Dundalk garda station in 1987.
From the first sessions in June 2011, I travelled to Dublin regularly for more than two years.
The tribunal's remit covered the murders of Chief Superintendent Harry Breen and Superintendent Bob Buchanan – but it soon became clear that Dundalk garda station had been at the centre of scores of incidents.
One of the most startling days came in June 2011 when eyewitnesses relived that traumatic day.
There could not have been a person in the hearing room who didn't shiver as Maurita Halpin broke down in tears. She dramatically recalled being ordered to lie face down on the ground by masked and armed men, before hearing the terrifying sound of a volley of gunfire, and then the bloodthirsty howls of triumph as Harry Breen lay dead on the road and Bob Buchanan dead in his car.
She also recounted eerie sounds coming from walkie talkies carried by the terrorists.
It emerged that this was how the IRA communicated in their murderous attacks, over CB radio with sounds, whistles or even just clicks of the radio, known by the army as 'gush'.
This gush was the closest the inquiry came to a smoking gun. It started at around 11.30am that morning, indicating when the IRA started preparing.
Judge Smithwick did not hesitate to work with anyone he thought might help, sending his legal team to meet former members of the Provisional IRA.
And the scores of RUC officers who travelled to Dublin to give evidence – even though they didn't legally have to – must be commended.