The hyponatraemia inquiry was first announced in 2004, following a TV documentary about the deaths of three children in Northern Ireland hospitals.
They died in separate incidents, but the programme alleged all three deaths - those of Lucy Crawford, Raychel Ferguson and Adam Strain - were a result of mistakes by staff as they administered intravenous fluids.
By 2008, the inquiry was extended to examine the cases of two more children - Claire Roberts and Conor Mitchell - who died while receiving hospital care.
All five children died at the Royal Belfast Hospital for Sick Children (RBHSC) between 1995 and 2003.
Hyponatraemia is a shortage of sodium in the blood that can be fatal.
The condition can occur when fluids are not administered properly and the issue of hospital fluids management is central to the work of the 14-year public inquiry.
The tribunal's remit also includes the examination of claims that hospital staff and one health care trust tried to cover up one of the five deaths.
The television documentary Insight: When Hospitals Kill is broadcast by UTV.
It alleges that three children - Lucy Crawford, Raychel Ferguson and Adam Strain - may have died due to mistakes by medical staff in hospitals in Northern Ireland.
The documentary raised concerns about the amount of fluids all three children had been given by hospital staff, alleging that errors in fluid management had led to their deaths.
It also alleged that health staff tried to cover up Lucy Crawford's accidental death.
Northern Ireland's direct rule health minister, Angela Smith, announces that she has appointed John O'Hara QC to conduct an inquiry into the issues raised by the documentary.
The Inquiry into Hyponatraemia-related Deaths is initially commissioned to examine the medical care and treatment given to Adam Strain, Lucy Crawford and Raychel Ferguson. The chairman is expected to produce a final report and recommendations by 1 June 2005.
The Police Service of Northern Ireland requests that the inquiry postpone its investigation into Lucy Crawford's case as it may compromise a police investigation into her death. The chairman agrees, but the inquiry continues to work on the cases of Raychel Ferguson and Adam Strain.
Police inform the inquiry team that they have also decided to investigate the deaths of Raychel Ferguson and Adam Strain. They request that public hearings be deferred and no further steps taken until the police investigations into all three deaths are complete.
An inquest into the hospital death of Belfast schoolgirl Claire Roberts opens. Two doctors tell the coroner that her case should be referred to the hyponatraemia inquiry.
The Public Prosecution Service (PPS) announces it has dropped its investigations into the deaths of Adam Strain and Lucy Crawford.
The Public Prosecution Service confirms that no-one is to be prosecuted over the death of Raychel Ferguson on 10 June 2001.
The hyponatraemia inquiry's remit is extended to examine the circumstances of the deaths of Claire Roberts and Conor Mitchell.
The chairman reveals that Lucy Crawford's parents have recently contacted him to say that for personal reasons, they do not want their daughter's death to be "considered in any way by the inquiry" and want all references to her to be removed from its work.
The chairman agrees to their request, but the inquiry is still required to investigate the aftermath of Lucy's death - particularly doctors' failure to identify the correct cause of the fatality and to what extent the alleged cover-up by health staff contributed to Raychel Ferguson's death 14 months later.
The inquiry is postponed again as the Belfast Health Trust reveals it has recovered documents that the inquiry team was previously told had been destroyed.
Raychel Ferguson's mother, Marie, calls on the inquiry chairman John O'Hara to resign after he announces that the hearings are to be further delayed due to new evidence. At this point, in the eight years since it was set up, the inquiry has only sat in full public session for one day.
The inquiry is told four-year-old Adam Strain was given an "inappropriate and massive" quantity of fluid during a kidney transplant operation at the Royal Belfast Hospital for Sick Children in 1995.
A new document is submitted to the inquiry that casts doubt on testimony given by senior clinicians about the death of Adam Strain. The document, written in 1995, suggests that some of the doctors who treated Adam knew that the donor kidney he was given had stopped working. The new evidence causes the inquiry to be postponed again, this time until September.
The parents of nine-year-old Claire Roberts weep in Banbridge courthouse as the inquiry is told their daughter had been given 300% more medication than the quantity prescribed for her.
Inquiry chairman John O'Hara QC launches a scathing verbal attack on the Belfast Health Trust after having to adjourn the hearings yet again. The latest postponement is a result of the trust's late submission of information, requested almost a year earlier. Mr O'Hara apologises to the families after the fourth adjournment of the inquiry in less than a year.
A senior doctor on duty the morning after Claire Roberts was admitted to the Royal Belfast Hospital for Sick Children tells the inquiry she cannot recall examining the child. Consultant paediatrician Dr Heather Steen said she had "little memory" of events for health reasons and "can't defend my notes or those of others".
Claire Roberts' parents accuse some senior health care staff of a cover-up over their daughter's death in 1996. The family's solicitor tells the inquiry that when an investigation into the child's death finally got under way 10 years later, "it looked as though a hand was steering the evidence from behind the scenes".
Consultant paediatrician Dr Heather Steen denies claims of a cover-up over the death of Claire Roberts, but admits there were numerous deficiencies in the child's care, including mistakes in the dosage of medication. Dr Steen tells the inquiry that staffing levels were dangerously low at the time and that, in hindsight, Claire's death should have been reported to the coroner.
A former chief executive of Belfast Health Trust, William McKee, admits to the inquiry that his organisation "failed Adam Strain and his family in the care management of his fluids". Mr McKee also said: "It's clear we failed Claire Roberts in her treatment and in the communication with her family, both before and after her death." However, he says he does not feel that, as chief executive, he should be held responsible for their deaths.
A senior doctor who oversaw the care of nine-year-old Raychel Ferguson at Altnagelvin Hospital in Londonderry admits to the inquiry that staff had "failed" the child. Consultant paediatrician Dr Brian McCord tells her family that he wanted to "professionally offer my apologies" for poor communication.
Dr McCord said the Fergusons had been given "false hope" which had added to their distress. Raychel's mother says she has waited 12 years for an apology and is grateful a doctor has finally admitted that the hospital failed her daughter.
One of the doctors who treated Lucy Crawford at Royal Belfast Hospital for Sick Children (RBHSC) admits that "an illogical set of causes of death" were put on the toddler's death certificate. Consultant paediatrician Dr Donncha Hanrahan also accepts that he handled the issuing of the death certificate very badly.
The court heard that despite hyponatraemia being mentioned on the autopsy form, which was completed by a different doctor, this information was not provided to the coroner, nor was it put on Lucy's death certificate. Dr Donncha Hanrahan also accepted that if more information had been provided to the coroner on the day of Lucy's death, including about hyponatraemia, it would have triggered an inquest.
For the first time during the hyponatraemia inquiry, a Northern Ireland health trust publicly admits liability over the death of one of the five children - Raychel Ferguson. The admission was made by the Western Health and Social Care Trust, which runs Altnagelvin Hospital in Derry. Raychel was administered a lethal dose of intravenous fluid after a routine appendix operation at the hospital in June 2001.
Belfast Health Trust publicly admits liability for the deaths of Claire Roberts and Adam Strain at the inquiry. The pair died 11 months apart while they were being treated at the Royal Belfast Hospital for Sick Children in the mid-1990s. A lawyer for the Belfast Health Trust said his client wanted to offer "a sincere apology for the shortcomings in the management of Claire's treatment".
During the hearing, it emerges that Belfast Health Trust had previously made a legal settlement with Adam's family but a confidentiality clause had prevented any details of the deal emerging. At the same hearing, the Southern Health Trust apologises to the family of Conor Mitchell after admitting that guidelines had not been followed when the teenager was treated in Craigavon Area Hospital, County Armagh, in 2003. However, the Southern Health Trust does not accept liability for Conor's death.
Conor Mitchell's family issue a statement describing an apology from the Southern Health Trust as "cynical". They accuse the trust of making "partial admissions" over his death. They say that the fact the admissions had been extracted after ten and a half years, and on the eve of hearings into elements of their son's treatment, adds to the cynicism.
Mr Justice O'Hara - the inquiry chairman who is now a High Court judge - says that the evidence he has heard so far makes it difficult not to believe there was a cover-up, because of how the deaths of all five children were recorded. He was responding to evidence by Northern Ireland's former top doctor Dr Henrietta Campbell, who held the position of chief medical officer from 1995 until 2006.
Dr Campbell says that, of the five child deaths under scrutiny, she was only informed of one death during her time in office. Dr Campbell admits the informal mechanism that was in place for reporting hospital deaths was not good enough and says she looks back on previous interviews she had given about the deaths with "deep regret". However, she says that she would never condone a cover-up.
The Belfast Health Trust formally apologises for the shortcomings in the care of all five children who died at the Royal Hospitals in Belfast. The trust's chief executive, Colm Donaghy, said on behalf of his organisation, he regrets most sincerely the pain and suffering experienced by the families of Adam Strain, Claire Roberts, Lucy Crawford, Raychel Ferguson and Conor Mitchell.
Mr Donaghy admits fluid management was "poor" and communication with families was "not sufficiently transparent". He also acknowledges that the way the trust handled litigation had added to the hurt and grief felt by the relatives. The families say the trust's apology has come too late.
The chairman gets approval to engage two experts to assist him by assessing his recommendations. Neither expert will have any input into the chairman's findings on what happened in the past. They will advise him on whether his draft recommendations are realistic, practical and achievable.
Raychel Ferguson's family is awarded £40,000 in compensation for her death following a ruling by the High Court in Belfast. Her parents describe the award as a "total insult" and an "absolute disgrace".
Her mother, Marie Ferguson, says it took the Western Health Trust 13 years to admit liability for Raychel's death and called for massive change to the system. She said "no amount of compensation" could ever replace her daughter.
The chairman says he will publish his report on 31 January 2018.
The public inquiry publishes allegations by a whistleblower who works for the Western Health Trust and raises questions about searches of a premises in the Western Health and Social Services Board in 2004.
A Health and Social Care Board's internal inquiry found that there was no evidence to suggest that information had been deliberately removed or that searches had not been carried out adequately.
A solicitor for one of the families says that once the inquiry publishes its findings, they will consider asking the police to investigate the whistleblower's claims.
The inquiry publishes its report. It finds that four of the deaths were avoidable.
In Conor Mitchell's case, the inquiry did not look at whether his death was avoidable or not.
The damning report is heavily critical of the "self-regulating and unmonitored" health service.
The Belfast, Southern and Western health trusts said they "unreservedly apologise" to the five families.
Mr Justice O'Hara is scathing of how the families were treated in the aftermath of the deaths and also of the evidence given to the inquiry by medical professionals.
The chairman said that the deaths of Adam Strain, Claire Roberts and Raychel Ferguson were the result of "negligent care".
He found that:
- while investigating the death of Adam Strain, the inquiry had been met with "defensiveness and deceit" and that "information was withheld" about what happened to Adam in the operating theatre
- there "was a cover up" in the death of Claire Roberts, whose death was not referred to the coroner immediately to "avoid scrutiny"
- poor care was "deliberately concealed" in the death of Lucy Crawford
- there was a "reluctance among clinicians to openly acknowledge failings" in the death of Raychel Ferguson
- in the death of Conor Mitchell, there was a "potentially dangerous variation in care and treatment afforded to young people at Craigavon Hospital"
Northern Ireland's Attorney General directs the coroner to open a fresh inquest into the death of Claire Roberts.
The move is welcomed by her parents, Alan and Jennifer, who for 21 years have protested that the truth about their nine-year-old daughter's death was concealed and that the findings of the inquest into her death were wrong.
A fresh inquest is due to begin into the death of Claire Roberts.
A preliminary hearing will take place at Laganside Courts in Belfast.