The Widgery Tribunal was the British government's immediate response to Bloody Sunday.
The day after the army had shot dead 13 protestors in Londonderry the Home Secretary, Reginald Maudling, announced there would be an inquiry and appointed the Lord Chief Justice, Lord Widgery, to lead it.
Many Irish nationalists were sceptical that a British tribunal held in Coleraine, a predominantly unionist town 30 miles from Londonderry, would be impartial.
The tribunal sat for just three weeks in February and March 1972, with the final report published on 18 April.
Lord Widgery concluded that the soldiers had been fired on first, and there was "no reason to suppose" that the soldiers would have opened fire otherwise.
He said there would have been no deaths had there not been an illegal march, which created a "highly dangerous situation in which a clash between demonstrators and the security forces was almost inevitable".
However there were inconsistencies in the report.
- The investigation found no conclusive proof that the dead or wounded were shot while handling a firearm, yet Lord Widgery concluded the soldiers had been fired on first. He also admitted the soldiers' firing "bordered on the reckless".
- Many important witnesses were not called to give evidence, and testimony was not taken from wounded survivors.
- The interpretation of the forensic evidence was flawed. Widgery concluded from firearms residue found on swabs taken from the bodies of the deceased that they had been in close contact with firearms. He dismissed any other explanations, including the possibility that the residue was due to transfer from soldiers or their vehicles.
- The possibility that victims were hit with gunfire directed into the Bogside from soldiers on the city walls was not given proper consideration.
The Widgery report was widely regarded as a whitewash, and relatives of the victims and nationalists campaigned for a new inquiry.
These campaigns were unsuccessful until 1997, when the Irish government submitted a detailed dossier of evidence to their British counterparts.
The 178-page document included many previously unconsidered witness statements, an assessment of fresh information about the shootings, and a damning indictment of the Widgery report.
The British government spent seven months studying the evidence before agreeing to a new investigation.
In January 1998 the prime minister, Tony Blair, announced an independent judicial inquiry into Bloody Sunday.
The prospect of a fresh investigation formed part of the peace process negotiations leading up to the Good Friday Agreement, and was viewed by many as a concession to Sinn Fein.
The inquiry would be headed by the British Law Lord, Lord Saville of Newdigate, and two judges from Commonwealth countries.
It would have the legal power to subpoena witnesses and compel the disclosure of documents and its findings would be made public.
Announcing the inquiry, Mr Blair acknowledged there had been flaws in the Widgery report.
"The timescale within which Lord Widgery produced his report means he was not able to consider all the evidence available.
"Since his report was published much new material has come to light about the events of that day.
"It is the interests of everyone that the truth is established and told."