London's Metropolitan Police Commissioner Sir Paul Stephenson has agreed to make public a report into the 1979 death of New Zealander Blair Peach, 33, who was killed as police were dispersing protesters during an anti-fascist protest.
Peach, a teacher and an anti-racist campaigner, died from a blow to the head at a demonstration against the National Front in Southall, west London, in April 1979.
A police commander at the time, John Cass, carried out an independent investigation and was reported to have recommended the prosecution of police officers, but no charges were ever brought.
Sir Paul agreed today that the report should be made public, after an unanimous call to do so by the Metropolitan Police Authority (MPA), the Guardian newspaper reported.
The decision was welcomed by Peach's family and partner, although no date has been set for the release.
Celia Stubbs, who was Peach's partner, said: "I'm totally bowled over, I was really cynical about it and I really didn't expect a result like this today."
Jenny Jones, an MPA member, proposed a motion calling on the police to publish the full report, written by Mr Cass, before the end of the year.
The report has remained secret despite requests for disclosure by Peach's family and friends, and an attempt by them last year to have access to it under freedom of information laws.
Ms Jones told a meeting of the MPA, chaired by London's mayor, Boris Johnson, and with Sir Paul in attendance, that the Met had declined to publish the report, suggesting that this was partly for the sake of the family.
"It is embarrassing keeping it secret," said Ms Jones. After other members voiced their support for publication, the mayor said it was clear that everyone was in favour of such a move.
"My starting point is a desire to publish," said Sir Paul, saying that he aimed to do so "as soon as I possibly can".
He said legal advice would have to be taken, but he was committed to such a course and agreed that the case for publication was "overwhelming".
Philip Peach, Blair's brother, who was at the meeting, welcomed the decision but said it would now be necessary to see how much of it was released.
"I could never understand why it wasn't disclosed originally," he said.
Previously police have said: "The Metropolitan Police has a duty of care to the family, and cannot act in a manner that could cause distress, where there is either a legal restriction or a reasonable justification for not doing so."
Mr Peach was reported at the time to have almost certainly been killed by a police officer, his skull crushed with an unauthorised weapon as he tried to walk home from an anti-fascist demonstration.
The death transformed Peach, an activist in the Anti-Nazi League, into a political martyr.
Ms Stubbs, now 68, said 11 witnesses claimed to have seen members of the Metropolitan Police Special Patrol Group (SPG) hitting Mr Peach in a side-street at the height of the violence.
An inquest recorded a verdict of death by misadventure, and police paid Stg75,000 ($NZ195,620) to Mr Peach's family in 1989.
Around the same time, lawyers were permitted to view SPG officers' notebooks, which have since gone missing.
John Cass, 84, has told the Guardian he is not opposed to his findings being made public. In 1979, then Commander Cass said his team of 30 investigators spent 30,000 man hours on the Peach case.
A pathologist's report into Peach's death said his broken skull was likely to have been caused by a lead-weighted rubber cash or hosepipe filled with lead shot.
Mr Cass was reported at the time to have identified a team of six SPG officers, at least one of whom he believed must have struck the fatal blow.
Recommending charges against the officers, his report was also said to include details of how officers lied to his investigators to cover up the attack.
NZPA