The killing of a man by a violent paranoid schizophrenic was the result of substandard care and failures in the health service, a report has said.
John Barrett repeatedly stabbed Denis Finnegan, 50, as he cycled in Richmond Park, south-west London, in 2004.
Poor communication and a lack of monitoring contributed to his escape from Springfield Hospital in Tooting, south London, according to a report.
Barrett pleaded guilty to manslaughter and was jailed for life in March 2005.
He had absconded from hospital the night before the killing in September 2004.
Barrett had been granted an hour's "ground leave" from the Shaftesbury Clinic, a secure unit within the hospital, but failed to return.
The decision to give him that freedom by consultant psychiatrist Dr Gill Mezey was described by the inquiry as "seriously flawed".
On leaving the hospital, 43-year-old Barrett bought numerous kitchen knives, took a taxi to Richmond Park and repeatedly stabbed Mr Finnegan, because he said he heard voices commanding him to kill.
The report, commissioned by the South West London Strategic Health Authority, was chaired by mental health solicitor Robert Robinson.
It said Barrett had received "substandard care", that "his risk to the public was not considered" and there were "systemic failures" in the service offered by the trust.
The finding said: "We do not say it was predictable that John Barrett would experience command hallucinations telling him to kill, but the risk of serious violence associated with deterioration in his mental state was known.
"We conclude that one of the factors that contributed to the killing of Denis Finnegan was that John Barrett's illness was inadequately treated."
The inquiry went on to question whether the Shaftesbury Clinic should even remain open as a secure unit.
The 400-page report gave details of Barrett's former violent history when he stabbed three people at a clinic in St George's Hospital in 2002.
Peter Houghton, who became chief executive of George's Mental Health NHS Trust after the killing, apologised to members of Mr Finnegan's family saying the trust was "deeply sorry".
Michael Howlett, from the mental health charity The Zito Trust, told a press conference the death was a result of an "appalling catalogue of errors".
"This is one of the worst reports, most critical reports, one of the most damning reports I have read in the past 10 to 12 years," he said.
He went on: "It beggars belief that John Barrett, who was a restricted patient under the responsibility of the Home Office for a very serious offence of violence, in which he very nearly killed a man in 2002, should have been granted a conditional discharge by a mental health review tribunal as early as 2003."
The report said Barrett's Responsible Medical Officer (RMO) did not even attend the hearing, nor were the Home Office's objections taken into account.
Mr Howlett asked the government to review how the mental health tribunals work.
A statement from Barrett's partner, know only as JW, read: "The unbelievable negligence of the trust snatched away from us the possibility of a happy future and with it the life of Denis Finnegan.
"This report is rightfully damning of the care and treatment provided by the trust to John, but what it can never do is give us back our lives."
Marjorie Wallace, chief executive of the charity Sane, said cases such as Barrett's were rare - around 40 murders a year are committed by people with mental illness - but the communication failures it exposed were not.
She said: "This is not just a question of changes to the law or of inadequate resources, it is a question of changing a culture which puts patient's rights ahead of those of their families and the community."
Anne Mackie, deputy director of public health for NHS London, said many changes had taken place to improve the performance of the trust and the trust's forensic service in the last two years but added that there was "still much to be done."
Former banker Mr Finnegan lived in Putney, south-west London, but was originally from Doncaster in South Yorkshire.