An inquiry has opened into the circumstances surrounding the death of Billy Wright, the founder of the Loyalist Volunteer Force (LVF), who was murdered in the Maze prison in December 1997. So how was he killed and what issues is the inquiry investigating?
Billy Wright was the LVF's leader in the Maze
The Billy Wright Inquiry is examining a number of failures in the months, days and hours leading up to his death at the hands of three members of the Irish National Liberation Army (INLA).
The inquiry was set up following an investigation by retired Canadian judge Peter Cory into allegations of collusion by the prison service and other authorities.
In March 1997 Billy Wright was sentenced to eight years in prison for making death threats against a woman, Gwen Read, on the Redmanville estate in Portadown.
He was initially sent to Maghaberry jail, which is west of Belfast, but in April 1997 he was transferred to the Maze prison, just outside Lisburn.
Two of his killers, INLA prisoners Christopher "Crip" McWilliams and John Kennaway, were also transferred to the Maze in May 1997 after being involved in a hostage-taking incident at Maghaberry.
The Maze was home to the notorious H-Blocks and shortly before Wright arrived the decision was taken to reserve C and D wings of H-Block 6 for members of the LVF and A and B wings for their arch-rivals in the INLA.
The practice of allowing H-Block wings to be segregated along paramilitary lines was common practice at the time. The Provisional IRA, UVF and UDA all had their own wings.
'Out of control'
There had been efforts to tighten up security at the Maze over the years. The most embarrassing incident was the breakout of 38 IRA prisoners in 1983.
But Alan Kane QC, counsel for Wright's father David, told the inquiry last week that by 1997 the Maze was a "monster out of control".
Among the matters the inquiry will be investigating is whether the prison authorities were aware of INLA threats to the life of Wright before his killing.
On the day he died - 27 December 1997 - Wright was due to receive a visit by his girlfriend Eleanor Reilly.
The Maze is about to redeveloped as a sports stadium
Because of the lay-out of the prison, inmates from H-Block 6 would be transported by van to the visitor centre.
The inquiry will be looking into the preparation of visitor lists to find out whether Wright's killers could have known in advance that he would be taken to the visitor centre.
It will also look into the question of why prison officer Raymond Hill was "stood down" from his post in the watchtower overlooking A and B wings on the morning of 27 December.
Another key question is why a CCTV camera overlooking the area had been out of action for several days without being repaired.
At 0940 GMT on Saturday 27 December a prison officer called Wright and fellow LVF member Norman Green to leave for the visitor centre.
McWilliams was later released under the Good Friday Agreement
Wright had just got into a prison van parked in the yard when three INLA men left their wing and walked out into the exercise yard.
Somehow they had smuggled two handguns into the prison - this will be another key issue for the inquiry to get to the bottom of - and two of the men were armed.
McWilliams had a .38 Markov semi-automatic pistol and John Glennon had a .22 Derringer.
They and Kennaway pushed open a section of wire fence that had been cut some time before. The hole had been held together with shoelaces and covered up by a stack of chairs to disguise it.
The three men then scrambled over the roof of A wing before dropping into the yard where the van was parked.
McWilliams opened the door of the van and shouted: "Armed INLA volunteers," before he and Glennon fired into the van.
Green and prison officer Stephen Sterritt cowered and tried to shield themselves but it was plain that the killers had picked out Wright as their target.
Freed under Good Friday Agreement
He tried to stand up and kick out at his assassins but was hit seven times and died almost instantly.
The three INLA men returned to their wing and later handed over the firearms before being arrested and later charged with murder.
Wright's killers, Chris McWilliams, John Glennon and John Kennaway were jailed for life but later released under the Good Friday Agreement.
Kennaway was returned to prison earlier this year and on Friday he was found dead in his cell at Maghaberry prison.
The inquiry will also be looking at the positioning of the prison van on the morning of 27 December and the decision to close the gates leading from the yard when the attackers were spotted.