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Thirty five years later, police are still hunting for the killer who left tragic Ann’s family “living in a nightmare from which they couldn’t wake up”.
Decades later the pain of her loss still casts a long shadow on her mother, Isobel, who last saw her daughter on November 18, 1986, after Ann had visited a family friend in hospital.
"She was just her normal self and I asked her if she'd still be down for Christmas,” said Isobel.
"She loved Christmas and would always come home on Christmas Eve and stay the night. We'd open one present on Christmas Eve."
That chat would be her last with Ann, who was a volunteer at a youth project and a heavy metal fan.
Time passed and the family heard nothing of their beautiful daughter and sister and they grew frantic with worry.
Isobel went to her flat and put notes through the door but still, no word.
It was a front page of the Evening News that brought the grim reality home. The body of a young woman had been found – news of which had given Ann's sister “a terrible sinking feeling”.
A few days later the family got the call they had all been dreading.
When Ann’s body was found 100 yards from her home on January 21 1987, the 20-year-old's remains were so badly decomposed a pathologist had to use dental records and a scar on her head to prove her identity.
Forensic tests revealed her body had been in the water for days – but she had been killed months earlier.
In another huge blow to her heartbroken family, they were told they couldn't see the body so never got to say goodbye. Instead, they were given a lock of her hair – a reminder of the beautiful, “happy go lucky” person they had been robbed of.
At the time of Ann’s murder, a manhunt was launched and a suspect was named in a report submitted to the procurator fiscal but there was not enough evidence to prosecute.
Police frogmen trawled the canal for clues and photographs were reportedly found scattered on a footpath near where Ann was found.
Twenty-five years after her death, Ann's devastated father, Graham, said he knew who had killed his daughter and that he has a picture of him sitting beside her at a family function - but could not reveal who it is due to legal reasons.
He believed his daughter was killed in a jealous rage because if this man could not have her, then "no one else could".
The suspect wasn’t publicly named but Isobel Ballantine, 74, and her husband Graham revealed his identity to detectives.
Despite a report to prosecutors and a cold case review, the man has never been charged and is believed to be still living in the Capital.
Graham previously said: "We know who it is but we're not allowed to say. He's a sociopath, he has to be."
However, former detective Chris Clark believes Ann may have been killed by the Beast of Bramley, John Taylor. Taylor is serving life for the 2000 murder of 16-year-old Leanne Tiernan and a series of sex attacks.
Detective Chief Inspector Brian Geddes of Homicide Governance and Review, said Ann’s murder would never be closed, and appealed to anyone with information to come forward and help give Ann’s loved ones the answers they have desperately sought for almost four decades.
"We understand how devastating it is for loved ones to not have the type of closure a conviction can help to bring. The death of Ann Ballantine is considered an unresolved murder and these cases are never closed,” he said.
"Police Scotland works closely with the Crown Office and Procurator Fiscal Service and meets regularly to review outstanding unresolved murders from across the country. Working collaboratively as the Homicide Governance Board, the potential for new investigative opportunities are regularly assessed to maximise the ability to deliver justice for grieving families, irrespective of the passage of time.
"Should any new information be received detectives in our Homicide Governance and Review team will thoroughly assess and consider for further investigation.
"Anyone who may have information about Ann’s death is urged to contact Police Scotland via 101 or contact the independent charity Crimestoppers anonymously on 0800 555 111."