A drug-fuelled social misfit who ferociously stabbed his grandmother to death and then attempted to murder a nine-year-old boy must spend at least 24 years behind bars a judge ordered today.

Bradford Crown Court heard that Nathaniel Flynn made Louisa Denby a cup of tea in her bedroom before stabbing her 50 times with a survival knife.

Flynn, 27, then went on a violent rampage thrusting a knife through the arm of schoolboy Jason D’Arcy in a skate board park in Shipley.

Flynn, who pleaded guilty to murder and attempted murder, was jailed for life by Mr Justice Keith today.

He will stay in prison until the parole board decide he is safe to be released but must spend a minimum of 24 years behind bars.

The court heard how Flynn ordered survival equipment on Amazon in the days before the killing.

Items included a carbon steel bushcraft knife, a camping-fishing knife, an SAS survival guide, a rope and a tarpaulin.

He was taking cannabis and tablets and had used class A drugs when living in the US.

The only account of the killing was when Flynn told a psychiatrist he gave his grandmother a cup of tea in her bedroom on July 1 and then attacked her.

“ I cut her throat and I thought it would be fast and she would die quickly like in the movies but she moved and I sprang on her and kept stabbing.

After the murder Flynn selected Jason at random as he played in the Carnegie Skate Park after school.

He said he followed the boy told him to come here, pulled a knife out of his pocket and went for Jason’s heart. The boy dodged the blow but the weapon cut into him to his sternum area. Jason put up his right arm to defend himself and Flyn drove the weapon right through it.

Jason ran home screaming and his dad Lee, a trained first aider, staunched the blood until paramedics arrived.

Jason was taken by Air Ambulance to Leeds General Infirmary where surgeons found an artery in his arm was divided and veins severed.

He needed a three-and-half hour operation to repair the wound.

Mr Justice Keith said Flynn was an entrenched drug user but: “Taking drugs was your lifestyle choice which means that you and you alone were responsible for what you did.”

Flynn claimed he killed his grandmother out of mercy because her mental health was deteriorating but other family members were clear that this was not the case.

“A likely explanation is that she just got on your nerves.”

The judge added she was vulnerable and she trusted you and you betrayed that trust by going into her bedroom and stabbing her to death.”

As well as the life sentence the judge sentenced Flynn to 14 years imprisonment for attempting to murder Jason, that sentence to run concurrently.