Ann Heron was found dead in a pool of blood at her Darlington home (Picture: PA/Metro.co.uk/Adam Williamson)

The air was hot on August 3, 1990.

Britain was experiencing a heatwave like no other, with wildfires and transport chaos up and down the country.

Ann Heron, originally from Glasgow, had decided to take advantage of the unseasonably warm summer at her home on the outskirts of Darlington in Durham.

The 44-year-old donned a bikini and stretched out on the grass as the sun beat down.

Her home – the ‘conspicuous’ Aeolian House on the A67 – was shared with her husband Peter Heron, who worked as a company director of a haulage firm nearby.

Ann was said to have been fearful of being home alone.

She often missed her children from her previous marriage, who were still living in Scotland.

But on August 3, her demeanour was nevertheless described as cheery by a friend who called her at 2.30pm.

Ann Heron’s body was found at her home near Darlington (Picture: North News & Pictures Ltd)

An hour later, a different friend on a passing bus spotted Ann sunbathing in her home’s front garden.

It was to be the last confirmed sighting of the mum alive.

For when husband Peter arrived home at 6pm, he discovered her body in a pool of blood in their living room.

She had a stab wound in her neck and her bikini bottoms had been removed.

The radio remained on, with her books and cigarettes found nearby, and the family dog was outside.

Peter said the front door had been open when he returned from home.

Frenzied investigations began as detectives tried to piece together what had led to Ann’s violent death.

Ann was said to feel unsafe at Aeolian House – and missed her children back in Scotland

But, 33 years later, no murder weapon or killed has been identified.

To mark the anniversary of her death Thursday, Ann’s son Ralph Cockburn released a statement on behalf of her family.

He said: ‘My sister Ann Marie and I want to express our gratitude to those who have already come forward with information. 

‘Your co-operation has been incredibly valuable, and we’ve made progress thanks to you. But we’re not there yet; we need your help to complete the picture. 

‘I know there are people out there who know something about what happened that day. You might think that the info you have is insignificant, but trust me, even the smallest detail could be a game-changer. 

‘It might just be that missing puzzle piece we need to finally catch our mum’s killer.’

During the investigation into Ann’s death, police said there were no signs of a struggle inside or outside the house.

Peter Heron, the husband of murder victim Ann Heron (Picture: North News & Pictures)

Such a situation could suggest the 44-year-old knew her killer, they suggested.

This theory was supported by the fact the family dog had not been heard barking, nor did it seem distressed.

Witnesses had initially reported seeing a blue Vauxhall Astra near the property, while others spoke of a blue Leyland Sherpa van.

When Heron’s murder was reconstructed on Crimewatch in October 1990, the multiple sightings of the blue car were described as ‘obviously the most interesting of the sightings.’

Police tracked down the owners of 3,500 blue cars, but the car has never been found or identified.

As is the case in many unsolved murders, attention had been quickly turned to Ann’s husband Peter.

One week after the murder, it was revealed that the 55-year-old with a 23-year-old barmaid at a nearby spa.

Data fuelled speculation that he may have been responsible for Ann’s death.

Witnesses said they saw a blue car parked outside the house, possibly a Vauxhall Astra (Picture: Rutger van der Maar)

Statistics show that 37% of women murdered in the UK are killed by their husband, boyfriend or lover.

Only 13% of women murdered in England and Wales in 1988 were murdered by strangers, with most women murdered at this time being killed in domestic violence situations.

Peter told police he had left a meeting at Cleveland Bridge at 4pm and drove a route back to his office through the village of Croft-on-Tees and Middleton St. George.

This wasn’t the most direct route, and police initially felt he had a missing amount of time which could not be accounted for between 4pm and 5.50pm.

Peter had remarried after Ann’s death and had always maintained his innocence.

But the case went cold throughout the years and the mystery was never solved.

There were false claims and more tip-offs but they led to dead ends.

The Northern Echo, the paper that serves the Darlington area, even received strange letters written from a person claiming to be Ann’s killer.

They read: ‘Hello editor, it’s me…Ann Heron’s killer!’ and ended ‘Your readers will have plenty to talk about. Signed The Killer.’

A 1990 Crimewatch documentary on the killing led to a wave of interest in the case but, still, no killer was identified.

In 2020, there were claims that an escaped prisoner in the area – Michael Benson – could have been responsible.

But after an investigation by Durham Constabulary, this was ruled out as they were ‘all but certain’ he was abroad at the time of the attack.

Channel 4 and Channel 5 have also ran documentaries on the murder in recent years.

Durham Police say they are continuing to use advances in forensic technology to review items recovered from Ann’s home in their search for answers.

Aeolian House is located off the A67 on the outskirts of Darlington, in County Durham (Picture: Google Maps)

Detective Chief Inspector Craig Rudd, of Durham Constabulary’s Major Crime Team, 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 using advances in forensic science in the hope of identifying evidence to prove who is responsible. 

‘I hope this appeal on the 33-year anniversary of Ann Heron’s murder will jog someone’s memory and they come forward with any information they may have. 

‘Ann’s family have been left devasted by what happened, they deserve closure, and we will never give up trying to find who killed her.’

Information can be reported to Durham Constabulary via 101, anonymously via Crimestoppers on 0800 555 111, or via the portal https://mipp.police.uk/operation/11HQ020101X43-PO1

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Ann Heron’s children are searching for the ‘missing puzzle piece’ on the anniversary of her death.