A cage fighter who murdered his ex-partner and tried to kill the 15-year-old boy with whom she was having sex has been jailed for 35 years.

Jealous ex-convict Paul Robson, 50, launched a terrifying and sustained attack on teacher Caroline Kayll, 47, and the teenager at her home in Linton, Northumberland last November.

Robson – who had blackmailed Mrs Kayll about her illegal relationship with the boy – kicked her in the head while wearing heavy work boots, and may have strangled her.

She could not survive the catastrophic brain injuries he inflicted.

O n Wednesday the cage fighting coach and former MMA fighter was sentenced at Newcastle Crown Court to life imprisonment with a minimum term of 35 years.

Passing sentence, Mr Justice Lavender did not accept there was any provocation for the attack, telling Robson: “You were upset when you learned of her relationship but you had known of it for over two weeks when you chose to drive from Glasgow to her home”.

Branded “a cruel and calculating coward” by the prosecution, Robson chopped off Mrs Kayll’s hair in clumps and slashed her on the buttocks.

He also repeatedly attacked the boy with scissors and a meat cleaver, sprayed them both with ammonia and stole their phones.

Nicholas Lumley QC, prosecuting, said: “He was never going to do anything other than ruin her.”

Robson, who has 21 convictions for 92 offences over more than 30 years, denied murder, claiming it was the boy who attacked Mrs Kayll, and said he struggled to get the better of the less powerfully-built teenager in the ensuing brawl.

The court heard that Robson had a clandestine relationship with Mrs Kayll while he was behind bars in HMP Northumberland.

They lived together but split up weeks before the murder and he blackmailed her when he found out about the illegal relationship she had started with the teenager, who cannot be identified.

She was to confide in a friend that Robson was blackmailing her for £35,000 and that her ex was “going to ruin her” and tell her school, the jury heard.

Over 10 days in November, she transferred £29,000 to Robson and took out a £10,500 loan, having previously been solvent.

On November 15, Robson drove three hours from Glasgow to Linton, having bought a locksmith’s bar, a magnetic GPS car tracker, screwdrivers, pliers, a wrench and the ammonia which he decanted into a washing-up liquid bottle.

CCTV showed him “prowling” outside her house.

Witnesses heard a female voice shout “get out” and later that evening Robson knocked on his former neighbour’s house to say “Caroline was in a bad way”, Mr Lumley said.

He then fled to Glasgow and remained at large while police made appeals to trace him before he was arrested.

Robson, who was convicted of murder, attempted murder and blackmail, went on the run for six days while his ex-partner’s life ebbed away in hospital.