11.30am UPDATE - Newton ordered to servce a minimum jail sentence of 16 years.

A delusional drug addict who stabbed a 75-year-old grandfather to death in a random attack has been jailed for life for murder.

After stabbing Philip Hendy and attacking another elderly man in Bristol, Stephen Newton, 41, told police he was Prince Charles's secret love child.

A jury at Bristol Crown Court found Newton guilty of murder after being asked to consider whether or not the amphetamine-user was aware of what he was doing at the time.

Newton, from Bristol, who previously admitted manslaughter with diminished responsibility, was sentenced to life in prison.

A hearing will be held at Bristol Crown Court today FRI to determine the minimum jail term Newton must serve.

Newton, who was high on amphetamine at the time of the attack, waited outside A and J News in Greenbank Road, Easton, for Mr Hendy to leave on April 29 last year.

He then followed the grandfather and stabbed him twice in the back and neck with a kitchen knife.

Newsagent's wife, Anita Jones, rushed out to confront Newton and helped Mr Hendy back into the shop where he collapsed.

Mr Hendy died on May 8 after fighting for his life in intensive care.

A short time after the stabbing, Newton followed Hargouindbhai Taylor, 84, on Spencer Park Road before punching him twice to the floor.

In an interview, Newton ranted for hours about several fantastical conspiracies.

He claimed the USA's President George W Bush, kidnapped his daughter and arranged for his son to have a sex change to look like Kylie Minogue.

He told police his son was murdered by Lord Woolf and the tunnels under the Elizabeth Shaw chocolate factory in Bristol were being used to abuse children.

Newton, who lived with his mother in Carlyle Road, Greenbank, claimed he was suffering from mental illness at the time.

But Stephen Mooney, prosecuting, told the jury Newton "was not suffering from a disease of the mind and should be found guilty of murder".

Mr Mooney said: "He killed Mr Hendy because he took the decision to take amphetamine knowing that when he was under their influence his decisions and thought processes were impaired.

"He is fully responsible for Mr Hendy's death morally and legally."

The jury heard Newton had a 15-year history of mental health problems including depression and a personality disorder.

He had seen several consultants and schizophrenia was considered – but no overall diagnosis was ever made.

Outside court, one of Mr Hendy's sons, Julian, 50, a company director, said: "The loss of our father has, for all of us, been a truly traumatic and devastating experience.

"We welcome the findings of the court that Mr Newton will now serve a lengthy sentence for his murder and that he will no longer be able to harm others by his irresponsible and selfish actions."

Mr Hendy said his family thought about his father every day, a wholly innocent man who was murdered by a complete stranger. He said: "There have been suggestions he was in the wrong place at the wrong time.

"Our family has lived in Greenbank for over 100 years. Our grandmother was born there, my father was born there, he went to school there, got married in the church there, and it is the place where he lived for all of his life. It is the place where we all grew up.

"My father had every right to pay his paper bill in Greenbank on April 29 last year. He was not in the wrong place at the wrong time – Mr Newton was."

Mr Hendy told how his family learned in court that Newton was well known to mental health services in Bristol and had a lengthy history of deception, drug abuse and offending.

"We learned there were clear warnings about his psychotic behaviour. We believe Mr Newton should not have been at liberty and dangerous in Greenbank that day, he should have been detained and in hospital."

Mr Hendy thanked newsagents Anita and the late John Jones as well as nurse Heather Chapman who tried to help his father on the day as well as surgeons at Frenchay Hospital who fought hard to save his father's life.