A teenager who stabbed his 15-year-old ex-girlfriend to death in the street has been detained for life with a minimum term of 17 years.

Logan MacPhail, then aged 16, stalked Holly Newton for an hour through Hexham, Northumberland, before knifing her 36 times in an alleyway.

CCTV showed him wearing a snood and a baseball cap and ducking out of sight as he followed Holly and her friends around the town centre.

Logan MacPhail, 17, who stalked and murdered Holly (Northumbria Police/PA)

He also stabbed a teenage boy who intervened to try to stop the attack.

He was convicted of murder following a trial at Newcastle Crown Court, and was sentenced at the same court on Friday.

Last month the judge lifted a reporting restriction which had prevented the media from identifying him due to his age.

The prosecution said MacPhail, who has autism and learning difficulties, did not accept that their 18-month relationship was over.

The night before he murdered Holly, he travelled 40 miles from his home in Gateshead to hers in Haltwhistle, Northumberland, where he hung around for hours.

MacPhail was eventually taken home by police who had been alerted by his mother that he was missing.

Holly’s mother, Micala Trussler, was concerned enough to contact the police and arranged to speak to an officer about MacPhail’s behaviour the next afternoon.

That same afternoon, MacPhail stabbed Holly to death.

MacPhail, who met Holly when they both attended Army cadets, claimed he never planned to attack her, but wanted to use the knife to kill himself – but the jury rejected his story.

CCTV image of Logan MacPhail speaking to Holly Newton in Hexham town centre before he fatally stabbed her (Northumbria Police)

In a victim statement on Thursday, Mrs Trussler described not being able to be with her fatally-injured daughter in hospital because her body “was a crime scene”.

The mother-of-four said Holly and MacPhail had a typical teenage relationship at first, but her daughter came to realise he was controlling her.

Mrs Trussler believed her daughter was the victim of domestic abuse, although she was under 16 at the time, and was caused emotional turmoil by her ex-partner.

He changed her social media passwords and made her believe he could hack into her accounts, as well as threatening to self-harm.

The night before the murder, MacPhail tried repeatedly to be allowed into Holly’s home and hung around for hours, trying to convince one of her siblings to open the door.

“I dread to think what could have happened to the rest of my family had he been allowed inside,” the mother said.

During the two-day sentencing exercise, there was discussion about MacPhail’s learning difficulties, his autism and his culpability.

David Brooke KC, prosecuting, pointed out the teenager was able to get to Haltwhistle from his home in Gateshead alone the night before the murder, to follow Holly around Hexham while disguised and to lie to her about his whereabouts.

“He was perfectly able to make rational choices,” Mr Brooke said.

Nigel Edwards KC, defending, said MacPhail’s progress since he has been in secure accommodation was “meteoric”.

MacPhail had admitted manslaughter, but was convicted of murder as well as wounding with intent on the teenage boy.