Paranoid schizophrenic John Barrett absconded from Springfield Hospital in Tooting, London, before stabbing Denis Finnegan who was riding his bike through Richmond Park.
The killing, on September 2, 2004, sparked a major independent inquiry, commissioned by the South West London Strategic Health Authority, into what went wrong.
The scathing 400-page report came 24 hours before the British Government publishes its Mental Health Bill designed to protect the mentally ill from harming themselves and others.
Its verdict was welcomed by the family of Mr Finnegan, a 50-year-old former Royal Bank of Scotland worker who had just returned from a career break.
The report criticised Dr Gill Mezey, who gave permission for Barrett to leave the Shaftesbury Clinic secure unit at Springfield for an hour’s “ground leave”.
Hearing voices in his head that commanded him to kill, 43-year-old Barrett left the hospital, bought a pack of kitchen knives and attacked Mr Finnegan the next day.
He pleaded guilty to manslaughter, was sentenced to life in March last year and is being treated at Broadmoor Hospital.
The inquiry described Dr Mezey’s decision to release him without assessment as “seriously flawed”.
It also noted insufficient monitoring of the patient, too much emphasis on his wishes rather than safety and poor communication between staff.