A convicted killer has been found guilty of murdering his wife six years before he went on to kill his fiancee.
Ian Stewart, 61, was accused of killing Diane Stewart in 2010 and was immediately handed a whole-life order after the jury of five men and seven women returned their verdict at Huntingdon Crown Court on Wednesday.
He was investigated for Mrs Stewart's murder following his 2017 conviction for killing his fiancee Helen Bailey, a children's book author, the year before.
Stewart killed 51-year-old Ms Bailey in 2016 and dumped her body in the cesspit of the £1.5 million home they shared in Royston in Hertfordshire. A trial at St Albans Crown Court heard it was most likely she was suffocated while sedated by drugs.
That investigation led to Stewart standing trial over the death of 47-year-old Mrs Stewart at their home in Bassingbourn, Cambridgeshire.
The cause of Mrs Stewart's death had been recorded at the time as Sudden Unexplained Death in Epilepsy (Sudep).
Stewart told his trial at Huntingdon Crown Court that he found Ms Stewart collapsed in the garden of their home in Bassingbourn when he returned from the supermarket.
He said he tried to revive her, attempted to contact neighbours who were a doctor and nurse, tried again to revive his wife, and then called 999.
He said he thought she had suffered an epileptic seizure.
Mrs Stewart had not had an epileptic fit for 18 years and took daily medication, jurors were told, with consultant neurologist Dr Christopher Derry estimating that her risk of having a fatal epileptic seizure was about one in 100,000.
During a 999 call Stewart was instructed to perform CPR on his wife and said he was doing so, but paramedic Spencer North, who attended the scene, said there “didn’t seem to be any effective CPR”.
Mrs Stewart’s death was not treated as suspicious at the time and, while a post-mortem examination was carried out, it was not a forensic post-mortem.
As part of the police investigation following Stewart’s 2017 murder conviction, consultant neuropathologist Professor Safa Al-Sarraj was asked to examine preserved parts of Mrs Stewart’s brain, which had been donated to medical science.
Prof Al-Sarraj said there was evidence that Mrs Stewart’s brain had suffered a lack of oxygen prior to her death, and he estimated that this happened over a period of 35 minutes to an hour.
Prosecutor Stuart Trimmer QC said Mrs Stewart’s death was “most likely caused by a prolonged restriction to her breathing from an outside source”, such as smothering or a neck hold.
Home Office pathologist Dr Nat Cary described SUDEP as a “diagnosis of exclusion”, adding that “an equal diagnosis of exclusion is having been put into such a state by some covert means – smothering or interfering with the mechanics of breathing or some kind of drug use”.
The court heard that full toxicology was not carried out as part of the 2010 routine post-mortem examination, and nor was a neck dissection.
Dr Cary said that, as in the case of Mrs Stewart, there was “no injury that was visible” in the case of Ms Bailey, who was in the cesspit for three months before she was found.
The court heard that Stewart received £96,607.37 after his wife’s death, in the form of £28,500.21 from a life insurance policy and the rest from bank accounts.
Both of the couple’s sons were out on the day of their mother’s death, with then 15-year-old Oliver at school and Jamie, then 18, taking his driving test.
Jamie Stewart had told the court that he recalled “raised voices… between my mother and father” when he was at home on study leave for A-levels the week his mother died.