The police discovered a scene of unimaginable horror when they entered the flat of Brian Cherry.

The 43-year-old had been dismembered and his arms and left leg were severed. There was more. The officers found that the convicted killer, Peter Bryan, had fried the brain of his victim in butter and eaten some of it off a plate.

Horror turned to anger for the families of the victim and another man that Bryan went on to kill while waiting for his trial, when it was discovered that the cannibal had been released from a high security hospital where he was sentenced for battering a woman to death.

The Old Bailey heard that he killed the men within months of each other, and wanted to go on killing to create the "buzz" he desired.

The court was told the defendant, who pleaded guilty to two charges of manslaughter on the grounds of diminished responsibility, had developed an urge to eat human flesh.

Bryan, who suffered paranoid schizophrenia and a personality disorder, was given two life sentences yesterday, and was told he would never be released because he was too dangerous.

Judge Giles Forrester said: "You killed on these last two occasions because it gave you a thrill and a feeling of power when you ate flesh. The violence on each occasion was extreme and unpredictable, accompanied by bizarre and sexual overtones."

Aftab Jafferjee, for the prosecution, said: "The last two killings have taken place when the defendant was under the care of the mental health regime which has manifestly failed to protect the public. That there was a significant failure within the mental health care regime in recognising the danger that the defendant presented is plain."

The court was told that the mental health system had let the public down after Bryan was released from Rampton special hospital in Nottinghamshire where he was sent after the manslaughter of a shop assistant in 1993.

In the first killing, Bryan had confronted his former boss at a clothing shop in Chelsea, west London, in a dispute over money. He ended up beating his employer's daughter, Nisha Sheth, to death with a hammer.

He was sent to Rampton in 1994 after admitting manslaughter, but was freed in 2001 after applying to a health review tribunal. Bryan was released into the care of a psychiatric social worker and psychiatrist.

After a spell in an east London hospital, he was allowed to live as a care-in-the-community outpatient under the charge of the East London and City Mental Health Trust.

Bryan was later transferred to an open psychiatric ward at Newham General Hospital after allegations that he had indecently assaulted a girl, aged 16. As a voluntary patient, Bryan was allowed to leave the locked ward.

On February 17 last year, within hours of a ward review of Bryan in which staff had said that they had no concerns regarding his mental state, Bryan killed Mr Cherry.

In the early evening Bryan visited Mr Cherry, a man he knew and who he had visited before, and beat him to death with a hammer at his flat in Walthamstow, east London.

He used knives to saw off his arms and left leg. When the police arrived Bryan had already fried some of Mr Cherry's brain. The court heard that Bryan told police: "I ate his brain with butter. It was really nice. I would have done someone else if you hadn't come along. I wanted their souls."

He also said that cannibalising human beings was like "eating the forbidden fruit" and that he believed human flesh was part of the "natural food chain", the court heard.

He was sent to Broadmoor special hospital but within two months attacked and killed a fellow patient, Richard Loudwell, 59. Loudwell was being held at Broadmoor after admitting killing a woman aged 89.

Relatives of Bryan and his victims blame the mental health system for the two latest deaths.

Sheila Foley, chief executive of the East London and The City Mental Health Trust, promised that services would be improved.