The actions of a paranoid schizophrenic from Littlehampton who stabbed a stranger to death were "neither predictable nor preventable", an investigation concluded today.

Father-of-three Daniel Quelch, 34, suffered 82 knife wounds during the frenzied attack in front of two of his children which began as he slept at his parents' bungalow 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.

Following the 2008 court case, Mr Quelch's parents Ernest and Barbara, who live near Maidenhead, Berkshire, described how their son's death had devastated their lives and called for Frankum not to be released into the community.

NHS South East Coast commissioned a report by Verita into the care and treatment of Frankum - named only in the report as Mr X - by the Sussex Partnership NHS Foundation Trust.

At the time of Mr Quelch's death, Frankum was living in a shared house in Littlehampton, 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 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."

The report criticised the speed of an internal investigation of the trust, which was critical of the actions of certain individuals when it reported back in November 2007.

"We find no evidence to criticise the judgments of the professionals concerned," it stated.

Frankum, now 28, was described as "vulnerable and passive" with no sign of being a danger to others.

But finding that Frankum's compliance with medication was "erratic", the report suggested a psychiatric nurse trained in the clozapine drug should have been his care co-ordinator rather than an occupational therapist, or at least had a formal role in monitoring him.

"Either of these arrangements would have allowed the nurse to evaluate Mr X's behaviour and ascertain how much of it was attributable to his compliance or otherwise with his prescribed medication,"

it read.

It stated that the failure to carry out a formal risk assessment when Frankum moved into the housing association property - which did not have staff based on-site - was "poor practice" but said it accepted the move was the "right move at the time".

The report set out a number of recommendations including that the trust should review its approach to investigating "serious untoward incidents", consider issuing guidance on how staff skills are matched to patients, and provide assurance that care teams have a "common understanding" of the factors that contribute to difficulties experienced by people with schizophrenia.

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.

"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."