A paranoid schizophrenic double-murderer who brutally killed a healthcare assistant to avoid being sent to a tougher no-smoking mental care unit with no wi-fi will never be released, a judge ruled today.

Ryan Matthews, 62, who believes he is possessed by the devil, was 31 years into a life sentence for killing two people when he twice stabbed grandmother Sharon Wall in the back at Gloucester's Wotton Lawn Hospital in July.

He had been due to be sent to the stricter Ty Catrin Hospital in Cardiff on the day of the killing and later told psychiatrists he would rather go back to prison than be sent to the non-smoking, internet-free Welsh unit.

Mrs Wall's family said they were waiting for answers from an ongoing Health and Safety Executive investigation into her death after Bristol Crown Court heard that the "much loved mother, grandmother, sister and aunt" should not have been alone on the "low secure" Montpellier Ward when she was killed.

Matthews, who was jailed at Exeter in 1983 under his former name Stephen Cecil King, had spent some time at Broadmoor before arriving at Wotton Lawn in 2012 and was considered so low risk he had been allowed out on a supervised trip into the community the day before the attack, Bristol Crown Court heard.

The killer, who had an antisocial behaviour disorder that made him become violent when he did not get his own way, had smuggled the murder weapon, a Sainsbury's kitchen knife, into the secure unit at least eight months before the killing, the court heard.

Sentencing Matthews to a whole life order, Mr Justice Davis told him that despite his schizophrenia and antisocial behaviour disorder "the process was under way for you to be released into the community".

He said the mental health patient was culpable for killing Mrs Wall, who had worked at Wotton Lawn for six years and with mental health patients for two decades.

The judge said: "The significance of that hospital unit in Wales is that the regime there was not to your liking. You couldn't smoke there, you couldn't have Internet access as much as you wanted. As you said to people at Wotton Lawn, you would rather go to prison instead.

"That is why you killed Sharon Wall."

Matthews' proposed move to the Welsh unit was sparked by problems with getting him to take his medication properly, the court heard.

As leather-jacket-wearing Matthews was led away Mr Justice Davis told Mrs Wall's family in the public gallery: "Obviously that man will never be released. Let us hope that he does not kill someone else in some other setting when he does not get his own way."

In a statement read outside court, Mrs Wall's family said she died doing something she loved, adding: "We take no satisfaction in Ryan Matthews' sentence today, as his life will not change from this. He has ruined our lives and no sentence will bring Sharon back to us.

"We would like to thank our family, friends and Gloucestershire Constabulary for their support during this dreadful time, however we eagerly await the findings of the investigations by the NHS and at the Health and Safety Executive to understand how this managed to happen to Sharon and what can be learnt from her death."

The 2gether NHS Foundation Trust, which runs Wotton Lawn, is improving search security at the unit in light of Mrs Wall's murder.

Speaking in Gloucester, Shaun Clee, its chief executive, said: "The search policies up and down the country on low secure units differ slightly. Our policies previously were in line with many other organisations' policies but we feel at this stage now, in the light of what has happened, that it would be appropriate to enhance those further."

The court heard that there should have been another healthcare worker with Mrs Wall as she did her morning rounds on the unit.

Richard Smith QC, prosecuting, said she was "unescorted and alone", adding: "The practice was that when the night shift ended and the day shift started, what was supposed to be a pair of healthcare assistants who would check the patients were in place and well.

"There was some doubt as to why Sharon was going through that process on her own that day."

Matthews told a psychiatrist after the murder that he had owned and kept the murder weapon "for his own protection" since November 2013, even making a plastic sheath for it, the court heard.

After being jailed as Stephen King, he later changed his name first to Steve James and then to Ryan Matthews, serving 16 years in prison before being sent to Broadmoor hospital in 1999 after being sectioned under the Mental Health Act.

The court heard he first spent time at the notorious high security unit in 1992 and was diagnosed as schizophrenic the following year.

Mr Smith added: "It is clear that was a planned move to Wales with which the defendant did not agree.

"He was unhappy that the new unit had a no-smoking policy and no wi-fi. On more than one occasion he said he wanted to stay where he was and said very clearly he would rather go to prison than go there.

"It seems that he decided to do something so demonstrably violent that he would not be moved to Wales and would get a return to prison that he had spoken of."