A report by Lord Saville into the events of Bloody Sunday in Derry 38 years ago was due to be handed to the Northern Ireland Secretary Owen Paterson this afternoon.
It will be published tomorrow afternoon, when British Prime Minister David Cameron will make a statement in the House of Commons.
Special arrangements have been made for relatives of the 14 people shot dead by paratroopers and for the soldiers and their representatives to see the report tomorrow morning.
The inquiry was announced in 1998 and became the longest-running in British legal history.
Bloody Sunday was one of the most controversial events of the troubles.
Thousands had participated in a civil rights march when Parachute regiment soldiers opened fire on the crowd in the Bogside, killing 13 people. Another victim died in hospital.
Following representations from the families and the Irish Government, Tony Blair agreed in 1998 to set up a fresh inquiry.
Nearly two years elapsed before three judges headed by Lord Saville began hearing evidence at the Guildhall in Derry.
There were over 900 witnesses, among them Sinn Féin's Martin McGuinness.
He denied firing the first shot on the day but confirmed he was then a prominent IRA member.
A previous report by Lord Widgery 11 weeks after the killings was widely regarded as a whitewash.
It said shots had been directed at the paratroopers before they started firing.
This time with the hearings switched to London because of security fears, Lord Saville took evidence from over 245 soldiers.
They included Lt Colonel Derek Wilford who led the paratroopers in Derry.
There was fresh controversy before the report was handed to the Northern Secretary when the Alliance leader David Ford, now Justice Minister, described the inquiry as pointless.
He met relatives to clarify his comments concerning the investigation costs of nearly £200m.
CoI urges positive projection
There has been a call from the Church of Ireland's leader in Derry for the city to project itself as a community which is growing in maturity and self-confidence.
In a statement, Bishop Ken Good said it was important that this positive image be portrayed as the world's media focused once again on what he called ‘our proud and historic city’.
In what he called ‘these pivotal days’, the Bishop Good said he hoped all Derry people would listen carefully to one another while paying careful attention to the findings of the Saville Report.
He said this was a time to show that the city had the desire and the will to deal courageously and humbly with issues that have long been painful and contentious.
And he urged individuals and the community to speak in measured, constructive and respectful tones given that, as with every death or injury, they were dealing with deep emotion and human pain.