A "DANGEROUS" mental health patient who stabbed a man with a 10-inch knife during an attempted armed robbery has been jailed.

Ricky Harris, of Pegasus Road, Oxford, had a history of mental illness and had been sectioned at the Warneford Hospital, in Oxford, twice before he tried to rob the Costcutter in Rose Hill, in the city, at knife point in January.

The court heard how have-a-go hero Nali Swar wrestled the knife-wielding 26-year-old to the ground, sustaining a deep cut to his arm in the struggle.

Judge Peter Ross said he was in no doubt the crime had taken place because Harris had taken himself off his medication a couple of weeks before the robbery at the store in The Oval.

Jailing Harris for eight years the judge told Oxford Crown Court yesterday, Harris' wild swing with the knife easily could have killed Mr Swar.

He added: "That this was a blind lunge with the knife gives this court such very grave concern.

"It was an absolute lottery as to where that knife might strike and it could so easily have been a fatal, mortal wound."

The judge said the handling of Harris' case by mental health services had not filled him with confidence, but he could not be sure if Harris had denied treatment or been turned away.

He added: "From the perspective of a member of the public they see a man who has been sectioned, who repeatedly sought assistance and was turned away, was unsupervised to the extent he was able to stop taking his medication with no one apparently noticing.

"Then someone who goes on to commit an extremely grave offence.

"But the truth is I'm not in a position to resolve the deep conflict."

Oxford Health NHS Foundation Trust spokeswoman Victoria Taylor said yesterday, patients were free to choose whether to engage with treatment or not.

She added: "When incidents such as this occur our normal practice is to invite the service user and carers where appropriate to be involved in an investigation of the incident.

"We conducted a thorough review following this incident and this did not highlight any failings in the care we provided."

The court heard Harris had gone into the store, pushed into the queue and threatened the worker at the till with a 10-inch kitchen knife on Wednesday, January 20.

Prosecutor Michael Roques said Mr Swar then grabbed Harris from behind by his wrist and chest and tried to wrestle him to the ground but was stabbed in the arm during the struggle.

He told the court, Harris was shouting racist abuse at the people holding him down, and then told officers "I don't need a solicitor, I am guilty, I have his blood on my hands".

After the hearing Judge Ross praised the bravery of Mr Swar and awarded him £1,000 for risking his life to tackle Harris.

He added: "He was prepared to put not just his health at risk but his life and seeking not just to protect himself but protect Mr Little who was being threatened."

Harris admitted attempted robbery, possessing a knife and unlawful at a hearing at the same court in May.

The court heard Harris assaulted his sister and stopped her from leaving the house because he heard Irish voices telling him she would die and grabbed a knife in Tesco and threatened to kill himself.

He had been sectioned in March 2011 and September last year, but was only diagnosed with an unstable personality disorder in October.

Claire Fraser, defending, said her client had gone to his GP and Oxford Health for help on numerous occasion, but was left in the lurch.

She added: "What his health records detail is him frequently going to his GP and asking for help, saying he is not coping. Little help was forthcoming. It seems they thought it was anxiety despite there being a family history of bipolar disorder."

Ms Fraser insisted her client was not dangerous because he was back on his medication and of previous good character.

But Judge Ross found Harris was a danger to the public and said only an extended sentence was enough to protect the public.

Harris will have to serve at least six years of that before being able to apply for parole and on release will face an extended licence of five years.