The master manipulator snared by the brain sample his first victim had donated to science 

Years before Ian Stewart murdered author Helen Bailey and disposed of her body in the cesspit at their Hertfordshire home, the family of his first wife feared he might already be a killer.

There was always something suspicious about the way 47-year-old Diane had died in the garden at the couple’s home in Bassingbourn, Cambridgeshire, in June 2010.

With no witnesses around on that hot summer’s day, Stewart was able to fool paramedics and police into believing that former school secretary Diane, who had previously suffered from mild epilepsy but had successfully controlled the condition for 18 years with medication, had suffered a fatal fit.

A coroner recorded a ‘sudden unexpected death in epilepsy’ and, at Stewart’s request, mother-of-two Diane was cremated.

No one noticed at the time that he had given differing accounts to neighbours of the events leading up to her death, telling some he had seen her through the window hanging out the washing moments before she collapsed, and others that he had ‘popped out for ten minutes’ to Tesco and returned home to find her lying half on, half off the patio.

For Diane’s family, who noticed his strange behaviour throughout this time, nothing quite added up. And when, in 2017, Stewart was convicted of murdering his new partner, 51-year-old Helen Bailey, Diane’s mother Noreen Lem said she wanted police to reinvestigate her eldest daughter’s death. 

She told the Mail at the time how uneasy she had felt after the death of her ‘happy and healthy daughter’ and spoke of the ‘terrible shock’ of learning her former son-in-law had killed the woman due to become his second wife.

Yesterday, at Huntingdon Crown Court, 61-year-old Stewart was found guilty of murdering school secretary Diane. But it is one of several agonising features of this terrible case that 88-year-old Noreen passed away in 2019 before seeing him brought to justice.

As Mr Justice Simon Bryan put it: ‘Your callous murder of your wife deprived your sons of a mother, Wendy of a sister and Diane’s mother of a daughter.

‘We have all heard how full of life Diane was. A caring mother, a loving wife, a real people person full of vitality and life who made life better for those around her. You cut short that life. It is clear from the moving victim impact statement from Diane’s sister what a terrible impact your actions have had on the family. As Wendy says, no mother should lose a daughter, and she was cruelly deprived of her daughter by your actions.’

Stewart’s guilty verdict also heaps further grief on Helen Bailey’s family. If he had been caught at the time of Diane’s death, he would not have been free to scour bereavement websites for wealthy widows, eventually settling upon Helen – whose husband John Sinfield had drowned in the sea as they holidayed together in the Bahamas in 2011.

That tragedy, which Helen described as the day she was a ‘wife at breakfast’ and a ‘widow by lunch’, set her on course to meet the man she referred to as ‘the gorgeous, grey-haired widower’ – but who, in reality, was already a cold-blooded killer.

For above all, as became clear once again over the past three weeks in court, evil Stewart is a prolific and practised liar.

Right from the start, said the prosecution, his claim that Diane suffered a seizure was a ‘cover story’ from a man ‘capable of extreme and callous violence’. If he hadn’t gone on to kill Helen in 2016, then his terrible crime would in all likelihood never have been discovered.

What finally nailed him, more than a decade on, was painstaking scientific evidence, along with a forensic deconstruction of the 999 call he made and statements from neighbours revealing the varying versions of events.

Because of her epilepsy Diane had stated that, in the event of her death, her brain could be used for scientific research. This meant that experts were able to examine it in microscopic detail.

Pathologists found evidence of ischemia – damage to the brain cells due to lack of oxygen. Three experts concluded that her death was ‘most likely caused by a prolonged restriction to her breathing from an outside source’.

One who gave evidence said that the damage would have occurred over a period of 35 minutes to an hour before her death, which was not sudden as Stewart claimed. Another said that the chance of Diane having a fatal seizure was around one in 100,000. As this crucial new medical evidence emerged, so Stewart adapted his version of events to fit the time frame.

He said that he delayed calling 999 for around 20 minutes after supposedly finding Diane collapsed on the floor.

‘There was a big panic going on at the time,’ he said. ‘It was a horrifying situation to be in. You can’t imagine being in that situation.’

He said he performed CPR on his wife, then ran across the road to knock at a house where a doctor and nurse lived before returning home to continue trying CPR. Only then did he call 999.

It was a ‘lying charade’, said CPS barrister Stuart Trimmer QC, who also prosecuted Stewart at his previous 2017 trial. No one saw Stewart leave the house that morning. No one saw him run across the road to the neighbour’s house.

‘You are a devious man,’ he added. In reality Diane was dead by the time Stewart called 999. He waited until he was certain she couldn’t be revived.

For more than 18 minutes, until paramedics and an air ambulance arrived at the Stewarts’ home, he kept up this despicable pretence.

During the recorded call played to court he can be heard panting down the phone, pretending to be in a state of panic but stopping and starting, letting the act slip. He was instructed to perform chest compressions, but despite having undertaken first aid training, complained at how difficult it was and said his wife was ‘blocked up’.

Paramedic Spencer North who arrived at the scene noted how calm and ‘dissociative’ Stewart was. There ‘didn’t seem to be any effective CPR’, he told the Court, ‘but we were told when he came out of the gate that he was just doing CPR.

‘Generally, effective CPR causes trauma. You crush the ribs, they pop, they snap, the airway is normally open.’ He said he saw blood-stained saliva on Diane’s mouth and, if there had been effective mouth-to-mouth, that would have been ‘everywhere’.

And yet PC Matt Gardner, who attended the scene, said that he did not assess the death as suspicious and so he filled out a coroner’s report form.

‘He answered my questions clearly,’ he said in evidence. ‘I wouldn’t say distressed, distraught, but people act very differently under such circumstances.’

Diane’s sister Wendy Bellamy-Lee told the court she always had concerns about the death. ‘There was an element of suspicion because Ian had been on his own,’ she said.

She called the coroner in the days after Diane died to ask for more information. Wendy said she ‘did not think it was fitting to ask a grieving husband how his wife had died’.

Stewart was furious when Wendy told him she’d contacted the coroner. ‘He was really, really cross with me,’ she told the court.

Clearly urgent questions remain about how easily the double killer managed to pull the wool over the eyes of police and pathologists, not to mention the coroner who concluded she died of natural causes.

The Mail has been given access to the documents from Diane’s one-day inquest held in chambers at Huntingdon on September 14 2010 by assistant coroner Belinda Cheney. It seems that her past history of seizures led experts, who knew nothing of the strange circumstances around her death, to conclude that epilepsy was the most likely cause.

The neuropathologist who examined Diane’s brain in the days after her death concluded that the signs of oxygen-starved cells he saw were likely to be due to the epilepsy recorded in Diane’s ‘provided history’.

He advised that his findings should be integrated with the ‘general post-mortem examination’ in assessing the cause of death, adding ‘if that does not reveal a toxicological cause or anatomical cause for death, “sudden unexpected death in epilepsy” should be considered’.

But a full toxicology report was not undertaken. Tests conducted three days after Diane’s death looked only for the drug she had been taking to control her epilepsy. It was found to be present at a normal, ‘therapeutic’ level.

Given that Stewart drugged Helen with sleeping pills in the run-up to her murder, the findings of a more thorough examination could have been highly significant.

Officially, Diane’s death was put down to a terrible but natural tragedy which left a family with young children in tatters.

In Bassingbourn, where the Stewarts were hugely popular, Diane was remembered as an adoring mother and a stalwart of the community. She had been a long-term committee member at the Bedfordshire and Cambridgeshire Wing Air Cadets’ Bassingbourn squadron where her sons, Jamie and Oliver, who were 18 and 15 at the time of her death, were members. Ian Stewart and Diane had met in 1981 when they were both undergraduates at the University of Salford in Greater Manchester, where he studied computer science and Diane studied German.

He embarked on a PhD at Cambridge University but eventually dropped out for a job as a computer technician. Stewart, who grew up in Letchworth in Hertfordshire, and Diane married near her home in Dronfield in Derbyshire in 1986 when he was 25 and she was 23.

After the birth of their eldest son, they bought a plot of land in Bassingbourn and lived in a caravan while building their dream home. But behind closed doors, all was not as rosy as it seemed.

Software manager Stewart was off work for lengthy periods of time because of long-term health problems, a legacy of accidents earlier in his life. At one stage his weight ballooned to 22 stone.

One of his relatives told me this week that as an 18-year-old he fell through a plate glass door at a leisure centre which left him with a scar on his face, which he later covered by growing a beard. In his twenties he also banged his head badly while running down stairs.

‘He became unwell after that and it was all traced back to him banging his head,’ said the relative.

Stewart suffers from myasthenia gravis, a rare autoimmune disease which causes muscular weakness and respiratory problems. Police believe he played on his health problems to exert control over Diane and then Helen.

Wendy Bellamy-Lee said that her sister Diane had tried to raise concerns about Stewart during a family swimming trip in the 1990s.

‘She was uncomfortable about something, like Ian expected more of her,’ she said. ‘I did not feel happy about what she was trying to tell me.’ The sisters were interrupted and ‘we did not get back to where the conversation was’.

Jamie, now 29, said his parents argued the week before Diane died and their voices were so loud he was unable to revise for his exams.

After the trial, Dept Supt Jerome Kent, who led the investigations into both women’s murders, described Stewart as a ‘master manipulator’ who ‘skilfully controlled them both in the same way by playing on his frailties and needs’.

Within 18 months of killing Diane, he had met Helen Bailey. Five years after that, she suffered the same fate as Diane.

Stewart was already serving a life sentence when, in 2018, he was told by police that he was being charged with Diane’s murder. He replied: ‘You’re joking!’ – exactly the same response he gave when he was arrested for Helen’s murder.

After Diane’s death, he received close to £100,000, including a £28,000 life insurance payout as well as money from Diane’s bank accounts. He later sold the family home in July 2014 for £530,000 and put some of that money towards the purchase of the £1.5million home in Royston, Hertfordshire, which he shared with Helen until he killed her.

The successful children’s author had assets of £3.3million and had changed her will to make Stewart the primary beneficiary.

Stewart told the court he didn’t need Diane’s money and it was ‘for the boys’ future’.

Indeed, he often turned to his two sons – ‘the lads’ as he used to call them, who sat in the public gallery throughout – throwing them beseeching looks, just as he did during his first trial.

While the judge chastised him for his utter lack of remorse and refusal to admit his crimes, Stewart kept twisting around to the spot, barely six feet away from his sons, desperately trying to catch their attention.

Both refused to look at him until the very last moment when he was taken away from the court. At that point, Jamie glared at his father.

As Mr Justice Simon Bryan put it, as he handed Stewart a whole life sentence yesterday: ‘How any father can act as you did defies comprehension.

‘For having faced the agony of watching their father jailed for murdering the woman who should have been their stepmother, both must now come to terms with the terrible truth that the father who still professes to love them also killed their mother in cold blood.’