Metropolitan police report released after 30 years says Blair Peach was most likely killed by elite riot squad officer

The anti-fascist protester Blair Peach was almost certainly killed by police at a demonstration in 1979, according to a secret report released today.

Documents published on the Metropolitan police's website shed new light on the death of Peach, a 33-year-old teacher from New Zealand, whose death marked one of the most controversial events in modern policing history.

A campaigner against the far right, Peach died from a blow to the head during a demonstration against the National Front in Southall, west London.

Sir Paul Stephenson, the Metropolitan police commissioner, said the report made "uncomfortable reading" but unequivocally accepted the finding that a Met officer was likely to be responsible for the death and expressed his "regret".

Peach's family have campaigned to see the crucial report for more than 30 years. It said it could "reasonably be concluded that a police officer struck the fatal blow". A police van carrying six officers was identified as having been at the scene when the fatal blow was struck.

The 130-page report was produced by Commander John Cass, who ran the Met's internal complaints bureau and led the investigation into Peach's death. It reveals:

• Peach was almost certainly killed by an officer from its elite riot squad, known as the Special Patrol Group (SPG). A number of witnesses said they saw him being struck by a police officer, and the report found that "there is no evidence to show he received the injury to the side of his head in any other way".

• Despite concluding Peach was killed by a police officer, Cass said there was insufficient evidence to charge any officer over the death, a decision echoed by the director of public prosecutions, to whom his report was delivered. An inquest into the death later returned a verdict of death by misadventure.

• Suspicions centred on the SPG carrier U.11, the first vehicle to arrive on Beechcroft Avenue, the street where Peach was found staggering around and concussed. Cass said there was an "indication" that one officer in particular, who first emerged from the carrier but whose name has been redacted from the report, was responsible.

• The criminal investigation into Peach's death was hampered by SPG officers, who Cass concluded had lied to him to cover up the actions of their colleagues. He "strongly recommended" that three officers should be charged with conspiracy to pervert the course of justice, giving detailed evidence to show how they were engaged in a "deliberate attempt to conceal the presence of the carrier at the scene at that time". None were ever charged.

• From the outset, the Cass investigation appeared unlikely to find an officer guilty. He defined Peach as a member of a "rebellious crowd" in his terms of reference, adding: "Without condoning the death I refer to Archbold 38th edition para 2528: 'In case of riot or rebellious assembly the officers endeavouring to disperse the riot are justified in killing them at common law if the riot cannot otherwise be suppressed'."

Along with the Cass report, the Met has released more than 3,000 pages of supporting forensic science documents, witness statements, interviews with officers and legal analysis.

They include all the detailed evidence gathered by police in the weeks and months after Peach was killed. The nature of his injuries led at least one pathologist to conclude Peach's skull was crushed with an unauthorised weapon, such as a lead-weighted cosh or police radio.

It was already known that when Cass raided lockers at the SPG headquarters he uncovered a stash of unauthorised weapons, including illegal truncheons, knives, two crowbars, a whip, a 3ft wooden stave and a lead-weighted leather stick.

One officer was caught trying to hide a metal cosh, although it was not the weapon that killed Peach. Another officer was found with a collection of Nazi regalia.

In his report, Cass said the arsenal of weapons caused him "grave concern", but claimed there was insufficient evidence to prosecute the officers involved.

A total of 14 witnesses told investigators they saw "a police officer hit the deceased on the head" but, according to Cass, there were discrepancies in their evidence and most could not identify the officer.

The Met has resisted publishing any material relating to the death of Peach for almost 30 years.

That decision was reversed last year after an investigation by the Guardian into the parallels between events surrounding Peach's death in April 1979 and the death of Ian Tomlinson, a 47-year-old newspaper vendor who died during last year's G20 protests in London.

Stephenson intervened to support the release of the report after Tomlinson's death.

Today the commissioner said he was sorry officers had behaved in the way described by Cass. "But I am particularly sorry that we haven't brought it to that definitive point where we can absolutely say what happened, why it happened, and what was the legitimacy or otherwise of that."

He said that, 31 years on, the Met was a "completely different" force, citing what he said were rigorous inquiries following the death of Tomlinson at last year's G20 protests.

Peach's long-term partner, Celia Stubbs, said she was "relieved" to see the report after so long. Along with relatives of Peach, and the officers named in the report, she first received the documents on Friday.

"This report totally vindicates what we have always believed – that Blair was killed by one of six officers from Unit 1 of the Special Patrol Group whose names have been in the public domain over all these years," she said.

Her lawyer, Raju Bhatt, said he was still examining the documents, but his initial reading indicated Cass had tried but struggled to "undermine" evidence suggesting one of his officers killed Peach.

"What I read in this report is a senior investigating officer desperately trying to explain away this death, but despite himself, he is driven by the weight of the evidence to conclude that the death was caused by one of his officers," he said.

Names of officers and witnesses are blanked out of the report, but their identities can easily be established from published material, including several unofficial reports into Peach's death and transcripts from his inquest, where several officers gave evidence.

Bhatt said friends of Peach would gather outside Scotland Yard today, and read out the names of the six suspected officers inside the SPG carrier U.11.

The names include five officers serving under Alan Murray, the SPG inspector in charge of the carrier. Aged 29 at the time at the time of the death, Murray resigned from the Met in anger at what he believed was an unfair inquiry by Cass.

Last night Murray, who is now a lecturer in corporate social responsibility at Sheffield University, declined to comment on the Cass report, saying he had not been given time to digest its findings.

Deborah Coles, co-director of Inquest, an organisation that was set up in 1981 partly in response to Peach's death and provides advice on contentious deaths, called on the Met commissioner to concede that the force was responsible for Peach's death.

"The whole police investigation into what happened on 23 April 1979 was clearly designed as an exercise in managing the fallout from the events of that iconic day in Southall, to exonerate police violence in the face of legitimate public protest," she said. "The echoes of that exercise sound across the decades to the events of the G20 protest and the death of Ian Tomlinson in 2009."