A man brutally murdered his partner after she had sex with his friend.

James McCarten flew into a rage when he discovered Anna Rosenberg, 43, in his bedroom with widower Alan McLean at his flat in Glasgow in May last year.

The killer left Ms Rosenberg, the daughter of a university professor, with more than 100 injuries after battering her to death.

McCarten, 51, then left his flat in Maryhill, Glasgow, to go and watch a boxing match on TV.

Details of the attack emerged as McCarten stood trial at the High Court in Glasgow.

He denied being a murderer and tearfully told the jury how he had loved Anna "so much" and had planned to marry her.

McCarten was found guilty, however, and now faces life in jail when he returns to the dock next month.

The trial heard how McCarten had been dating Anna for around 18 months. The mother had a house in Bearsden, East Dunbartonshire, but often spent time at her boyfriend's flat.

She was described as a keen gym-goer who would "not harm a fly".

Last year, McCarten allowed fellow builder Alan McLean to stay with him after he had split from his lover.

The 62-year-old told how he and the mother had sex in McCarten's bed while he was out on May 2 last year.

The pair were stunned when they suddenly heard McCarten return home.

He arrived to find his friend hastily trying to put his clothes on while a terrified Anna lay in the bed.

McLean recalled: "He was shouting and bawling: 'how could you do this to me?'

"Anna kept saying she was sorry, she was crying. James was upset but that was understandable."

McLean said McCarten went on to headbutt him after asking him to take his glasses off.

He then kicked his friend out before launching a murderous attack on Anna. He repeatedly punched and kicked his petrified lover leaving the flat covered in blood.

The trial heard Ms Rosenberg, who he also tried to throttle, suffered 122 injuries including multiple fractured ribs. McCarten went on to walk out his flat to watch a boxing match at a friend's house.

McCarten claimed it was the next day when he returned that he realised Ms Rosenberg was dead. In a 999 call, he said his partner was "not right" and "would not wake up".

The court heard he tried to clean up the property and put clothes on a naked Anna. He gave evidence during the trial and repeatedly sobbed: "Why would I murder the girl?"

McCarten admitted being responsible for the death but insisted he did not "realise the extent" of his savage attack.

He said before the killing May 2 had been a "happy day" after getting a new job and he had also bought a pup for Anna.

McCarten said he got a "terrible shock" when he walked in on his friend and Anna, adding: "I thought: How could two people who are meant to love you do that?"

McCarten admitted he "saw red" and "unleashed" a "lot of blows" on Anna.

The killer insisted when he initially left his home, he did not believe Anna was dead.

McCarten said he knew he had "destroyed" his lover's family, adding: "I was happy that day, joy ... why would I murder someone when life was great?"

"I should not have done it - I should just have thrown the pair of them out."

Prosecutor Tim Niven Smith put to him that Anna had been "pummelled to a pulp", adding McCarten was someone who appeared "easily riled".

McCarten was also convicted of assaulting McLean as well as a separate charge of attempting to defeat the ends of justice.

Detective inspector Mark Bell from the Major Investigation Team: "A woman has needlessly lost her life and a family has been left devastated by the loss of a treasured loved one due to the selfish actions of McCarten.

"Anna died as a result of the selfish brutality inflicted on her by her partner. There is no place in a modern, progressive society for this type of abuse.

"I would like to pay tribute to Anna's family and friends who have shown great courage and dignity throughout this ordeal.

"Nothing can be done to reverse what happened on that day, however I sincerely hope that today's verdict will bring some small degree of comfort to Anna's family and friends."