This week it was revealed that the cost for the Bloody Sunday inquiry now stood at £181.2m, making it the longest and most costly in British legal history. The BBC's Ireland correspondent Denis Murray looks at Lord Saville's probe into events in Northern Ireland more than 30 years ago.
Why is the inquiry taking place?
The Bloody Sunday enquiry was set up in 1998 by then Prime Minister Tony Blair to re-examine the events of 30 January 1972, when soldiers of the Parachute Regiment shot dead 14 people attending a civil rights march in Londonderry.
The tribunal chairman is Lord Saville of Newdigate, alongside two other judges from Australia and Canada.
Bloody Sunday is one of the best-remembered events in the entire history of the Northern Ireland Troubles.
It was regarded certainly by the Catholic population as no less than mass murder, and badly damaged Britain's reputation abroad. The British Embassy in Dublin was burned to the ground by rioters three days later.
An initial inquiry under Lord Widgery was regarded by the Catholic community as a whitewash. The decision to hold a new inquiry was based on "the weight of new material available".
What developments have taken place?
Lord Saville made his opening statement in April 1998, and the inquiry's oral hearings began at the Guildhall in Derry, in March 2000, with an opening statement by counsel to the inquiry, Christopher Clarke QC.
This alone lasted up to the end of June, becoming the longest opening in UK legal history.
At one stage, the tribunal moved to the Central Hall, Westminster, after the Court of Appeal ruled that the evidence of soldier witnesses should not be heard in Derry because of fears for their safety.
Some of the soldier witnesses gave evidence from behind a screen, visible only to the three judges and legal teams.
The first witness was heard in November 2000, and the last in January 2005.
Why has it taken so long and cost so much?
Northern Ireland Secretary Shaun Woodward, in a written parliamentary answer earlier this week, said his receiving of the tribunal's completed report was not "imminent."
A spokesman for the tribunal pointed to the sheer scale of the operation - 2,500 witness statements, of whom 922 were called to give direct evidence.
One of those witnesses was Martin McGuinness, now deputy first minister of Northern Ireland, who accepted in evidence that he was the second-in-command of the Derry Brigade of the IRA at the time of Bloody Sunday.
There were also 160 volumes of evidence, containing an estimated 20-30 million words, plus 121 audio tapes and 110 video tapes.
What is the current situation?
The tribunal spokesperson said they stood by their last news release in August 2005 which said the "very large quantity of material" meant "it is not possible...to give any firm estimate of when the report is likely to be finished".
Most of the cost is in legal fees, but the way it was run was used as a template for both the inquest into the Omagh bombing of 1998, and the Hutton inquiry into the death of weapons expert David Kelly.
The cost is obviously way beyond what the government had expected, and means that other inquiries into events of the past in Northern Ireland - such as the Billy Wright Inquiry, which started last year - are likely to have much tighter purse strings.
Do the relatives think it will all be worth it?
Jean Hegarty, whose brother Kevin McElhinney was one of those killed on Bloody Sunday, says she will not know the answer to that question until the final report is made public.
She told me: "It's not the truth that has cost so much, it's the lies. If the British army hadn't lied on Bloody Sunday itself, there would have been no need for this inquiry."
She also said that Lord Saville and his colleagues had done their best to get at the truth. "You can't put a price on it," she said.
Interested parties will get some months notice of the report's completion, which will be delivered to the Northern Ireland secretary before publication.