ON the hottest day of the year Ann Heron spent the best part of the afternoon sunbathing in a bikini in her front garden. What happened next to the ‘mild-mannered and caring’ mum, 44, still remains shrouded in mystery. Less than three hours after she was last seen alive, Ann was found in her living room by her husband with her throat slit. She suffered four stab wounds to her neck, inflicted possibly by a scalpel, Stanley knife or razor, and her bikini bottoms had been removed. However, it was later confirmed she had not been sexually assaulted. The apparently motiveless murder prompted the biggest ever manhunt mounted by Durham Police, involving 65,000 man-hours, 4,500 statements and 4,061 interviews in the first few months. But there was still no weapon found and no answers as to who killed Ann and why. Thirty-five years on from the brutal killing the case remains unsolved. Described as the ‘softest person you could ever meet’, Ann was a grandmother to two boys, loved children and animals and had no enemies. She worked part-time in a care home. No-one had a bad word to say about her, and her death continues to raise the question as to why such a well loved woman endured such a brutal end. Ann's final hours Born Mary Ann O’Neill in Glasgow, by 1986 Ann was living on the outskirts of Darlington, County Durham in a £300,000 property named Aeolian House with her second husband, Peter Heron. She had moved to England earlier in the 1980s after separating from her first husband, Ralph Cockburn, leaving her three adult children, Ralph Jnr, Michael and Ann Marie, in Scotland. On August 3, 1990, Ann had been shopping with a friend in Darlington before returning home to have lunch with Peter, 55 at the time – something they did every day. Someone out there must know who did this to my mum and, more importantly, why.Ralph Jnr, Ann's son She told him her plans to sunbathe in the back garden. At 2pm, he returned to work as a company director for a haulage company and Ann spoke to a friend on the phone until 2.30pm who later described her as "cheery". By 3.30pm, Ann had moved to sunbathe in the front garden after a tractor had blown grass over the back and she was seen by a friend who was on a bus as it passed her house. Tragically, it was the last time she was seen alive. Grim discovery When Peter returned home at 6pm, he found their dog, Heidi, still outside, the front door open and Ann lying in a pool of blood in the living room. Police believed she was killed around 5pm and with no signs of a struggle, it’s thought Ann knew the culprit. Peter would later tell a press conference it was “impossible” to describe the horrifying discovery. He said: “We were only married for four years and they were the best years of my life. “She was the most placid and loveable person you could meet. Why would anyone want to kill her?” Mysterious blue car Initially police focused on a blue car – possibly a Vauxhall Astra or Leyland Sherpa van – that was seen by two independent witnesses. One saw a blue car parked outside the house at about 4.45pm while another saw a blue car driving at speed down the drive around 5.05pm. Both witnesses described the driver as dark haired, suntanned and in his early 30s. One of these was Liz Lamb, a 14-year-old girl at the time, who would later go on to feature in a documentary, ‘The Mysterious Murder of Ann Heron’ which aired on Channel 5 in May 2022. Now a senior lecturer in Journalism at the University of Sunderland, Liz told the documentary: “Aged 14, I was interviewed by police as a potential witness in the Ann Heron murder case. “On the day of the murder, I saw a blue car, driven by a man, leaving the murder victim’s house at speed.” Durham Police tracked down the owners of 3,500 vehicles which matched the description of the blue car but the investigation moved no further forward. In 1994, the 'alleged killer' penned a letter to local newspaper the Northern Echo, claiming responsibility for Ann's death, but no further developments followed. Husband's secret Ann’s husband, Peter, also came under scrutiny by the police, the press and the public in the aftermath of her death. He told detectives he had left a meeting at Cleveland Bridge at 4pm and drove – in his blue Mercedes – back to his office through the village of Croft-on-Tees and Middleton St. George. Police noted it wasn’t the most direct route and, days after the murder, it emerged he had been having a ten-month affair with a 32-year-old barmaid at his golf club. Two years after Ann’s death, Peter married a telephonist called Freda, whom he'd met on a work trip to Scotland. Peter – who has always maintained his innocence – told the Northern Echo, in 1995: “I know there are people who still think I killed my wife. One day the murderer or whoever is protecting him will crack. “No-one can live with that on their conscience.” DNA break-through By 2005, 15 years after the killing, new technology allowed for further DNA testing to take place and, after Peter’s semen was found in samples taken from his wife’s throat, he was charged with her murder. Peter, then 70 and a widower for the second time after his third wife died from cancer, had relocated to Wishaw, Lanarkshire and was due to plead not guilty at a subsequent hearing. However, four months later the case against him was dropped due to a lack of evidence and his family later described the ordeal as a "serious injustice". Sadly, Ann’s second son, Michael, passed away in 2011. Her two other children, Ralph Jnr and Ann Marie, have since made multiple appeals for information on key anniversaries. Heartbreaking pleas In 2010, 20 years after her mother’s death, Ann Marie said she struggled to understand how her mum’s killer was still at large. “What was the purpose of this unlawful killing?” she asked. “Someone out there has the answer. All I would ask is that they try and imagine being in our shoes and the torment as a family we have had to go through year after year.” Ten years later, in 2020, Ralph Jnr also made an emotional appeal for more information on the death of his mother. The former Strathclyde police officer said: “She was the softest person you could ever meet and she loved animals and children. “She has five grandchildren, three of which she never got the chance to meet, and four great-grandchildren that she has also never met. “Someone out there must know who did this to my mum and, more importantly, why. “If someone knows who did this and is withholding vital evidence, then I would urge them to rethink where their loyalties lie and do the right thing so my sister and I can finally get justice for mum.” Detective Superintendent Craig Rudd, from Durham Constabulary, said: “The investigation into the murder of Ann Heron remains open. “The Major Crime Team continues to review the case and investigate any new information.” Anyone with information can call 101 or contact Crimestoppers anonymously on 0800 555 111.