The family of a father of three who was stabbed to death in a random attack by a paranoid schizophrenic today condemned an investigation into the mental health care of the killer as "deeply flawed".
Daniel Quelch, 33, suffered 82 knife wounds during the frenzied attack in front of two of his children which began as he slept at his parents' bungalow near Maidenhead, Berkshire, in August 2007.
Benjamin Frankum was arrested at the scene, telling police he had been sent by MI5 to kill Mr Quelch, but he was ruled unfit to stand trial for murder.
Jurors at Reading Crown Court were instead asked to decide whether he was responsible for the killing, which they did after just over an hour of deliberations.
Frankum, who had been in and out of hospital with mental illness since 2001, was ordered to be detained in Broadmoor Hospital, where he remains.
A report today concluded that Mr Quelch's death was "neither predictable nor preventable".
NHS South East Coast commissioned the investigation by Verita into the care and treatment of Frankum - named only in the report as Mr X - by the Sussex Partnership NHS Foundation Trust.
Following the publication, Mr Quelch's parents Ernie, 66, and Barbara, 62, - joined by elder son Robert Quelch, 42 - described how their son's death had devastated their lives and said they believed the inquiry was a "missed opportunity" to prevent further loss of life by mentally ill people.
"We believe this is a deeply flawed inquiry," Mrs Quelch said. "It does not meet best practice, it did not talk to all the possible witnesses, it is in part inaccurate, and some of the findings are clearly not substantiated by the available evidence.
"We are fully aware that nothing now can bring Daniel back.
"But we are determined as a family to do everything we can to ensure that, as far as possible, no other family has to go through what our family has had suffer and endure."
At the time of Mr Quelch's death, Frankum was living in a shared house in Littlehampton, West Sussex, supported by a housing association after moving out of a residential home in May 2007 where he had been cared for since leaving hospital in the summer of 2006.
Frankum, who had a history of cannabis use, was diagnosed with "treatment resistant" schizophrenia but over the years doctors had identified a combination of medications which helped control some of his symptoms.
During the summer of 2007, Frankum's family, the housing association and care services were "increasingly concerned" about his behaviour, according to the report.
But professional teams decided the situation did not justify sectioning him.
The investigators said that although they identified a "number of failings and weaknesses in the actions of the statutory services during 2007" they could find "no link" between those and Frankum's actions on August 23, 2007.
"For the reasons that we set out in detail in the report we consider that the homicide was neither predictable nor preventable," it concluded.
"We conclude that there was no reason for the professionals to predict that Mr X was a risk to others.
"We consider that nothing professionals should have done would have prevented the homicide."
Frankum, now 28, was described as "vulnerable and passive" with no sign of being a danger to others.
Although the report stated that Frankum's compliance with medication was "erratic", it said his move out of fully-staffed accommodation to the housing association property was the "right move at the time".
But Mrs Quelch said there was no system in place to ensure Frankum took his medication and said there was a lack of monitoring and support, in particular when he was noticeably deteriorating.
She criticised the fact he was not detained under the Mental Health Act despite "serious and persistent" fears about his health and compliance with medication.
"We find it hard to see that Frankum received any appropriate care by mental health services," she said. "When he was in greatest need they appear to have simply wrung their hands of him and decided there was nothing they could do.
"We believe there were repeated failings in the care of Benjamin Frankum, yet today's inquiry asserts that Daniel's death was not preventable.
"We do not accept this finding."
Mr and Mrs Quelch said they had never been able to go back inside what had been their cherished family home for more than 20 years after what happened and had moved from one rented home to another as they try to sell the property.
Report author Lucy Scott-Moncrieff said: "Although we found areas where Mr X's care could have been better, we could find no evidence that the killing could have been predicted or prevented.
"We carefully examined all the evidence from the time Mr X was first admitted to see whether there were any signs that could have alerted staff that he might become violent.
"We found no evidence in his past that showed he was a threat to anyone else."
The fact that someone was not taking medication was not grounds itself for detention under the Mental Health Act, she added, although it would be a trigger for deciding whether there should be a full assessment.
Dr Shakil Malik, clinical director and consultant psychiatrist for the Sussex Partnership NHS Foundation Trust, said the trust had acted on recommendations set out in the report.
These actions included issuing new guidance to staff and providing assurances about the working methods of its new recovery teams.
"I would like to conclude by saying once again this was a tragic and exceptional case," he said. "It's important for us to remember that one in four people will have a mental health problem at some point in their lives yet very few of these people ever commit acts of violence.
"This said, it's right that our thoughts today should be with the victim and those who have been most seriously affected by his death."