A BLACK widower has today been convicted of murdering his first wife six years before he strangled his fiancee to get his hands on her fortune.

       Ian Stewart, 61, killed Diane Stewart, 47, on the back patio of the home she shared with him and their two sons in Bassingbourn, Cambs, in 2010.

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       Diane Stewart died at the family home in Cambridgeshire 7

       Ian Stewart murdered his partner Helen Bailey

       The deceitful monster was able to "fool" medics into believing his wife had suffered a sudden unexplained death through epilepsy.

       But in a "stroke of fortune", Diane had donated her brain for research - with experts finding she had been either suffocated or strangled.

       Stewart has now been convicted of murder following a trial at Huntingdon Crown Court.

       The double killer murdered Diane six years before he set his sights on vulnerable children's author Helen Bailey.

       He portrayed himself as a grieving widower still struggling with his wife's death to sign up for an online bereavement group.

       Helen, who had lost her husband in a tragic accident in Barbados, moved Stewart into her lavish ￡1.4million home.

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       But he started to drug her with sleeping pills after hatching a murderous plot to get his hands on the successful children's author's ￡4million fortune.

       On April 11, 2016, he smothered Helen to death then dumped her and beloved pooch Boris into a cesspit full of excrement fearing she had caught on.

       After Stewart was jailed over that "particularly callous crime", police began re-examining Diane's death.

       Diane's remains had been cremated but her brain was donated to medical research and brain tissue was also kept.

       From this, scientists were able to determine her chances of dying from epilepsy were more than one in 100,000, it was said.

       Diane had not suffered a seizure for 18 years and it was an "extremely low" chance her "mild" epilepsy killed her.

       Her brain also showed evidence of ischemia - when the brain is starved of oxygen for up to an hour.

       DOUBLE KILLER

       Stewart had been alone with Diane when he claimed he returned from Tesco to find her "twisted" on the back patio of their home.

       He then called 999, telling them: "My wife has had a fit. I think she has died".

       When paramedics arrived at the home, they discovered Diane without a heartbeat.

       While being quizzed by police, Stewart shrugged as he was asked about his wife's death.

       An officer asks: "Right - what was her cause of death?"

       Stewart, who sits with his back against the wall, quickly moves his shoulders up as he replies: "Epilepsy. Well, that's what the doctors told me."

       A second clip shows Stewart being asked what he died when Diane fell unconscious.

       He ignores a series of questions on if he did anything to bring her around, or whether he checked if she was breathing or not, simply rubbing his ear and looking away.

       The detective then asks: "How did you check if she was breathing - if you did?"

       Stewart shrugs again and plays with his beard.

       He continues to ignore all the officer's questions.

       In a final clip, he is asked ten questions in a row before replying: "No comment."

       The monster could also be seen gasping "you're joking" as police arrested him on suspicion of murdering Diane.

       MONSTER

       Despite his efforts to cover up the crime, suspicions were aroused by Stewart's behaviour after his wife's death.

       The monster received a total of ￡96,607.37 following the death of his wife from her bank accounts and ￡28,500.21 from a life insurance policy.

       He treated himself to a sports car and began embarking on new relationships in behaviour "hard to square with the conduct of a grieving husband".

       But one of his new relationships led to his downfall when he brutally murdered Helen in April 2016.

       Both killings bore chilling similarities - with both unwitting victims murdered at a home they shared with Stewart.

       He also showed a "willingness" to cover up the killings both times.

       While he was serving a minimum prison sentence of 34 years for Helen's murder, Stewart was charged with killing Diane.

       He will be sentenced at a later date.

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       Diane pictured with Stewart and sons Jamie and Oliver 7

       This is the creepy moment double murderer Ian Stewart simply shrugged a shoulder as he was asked about the death of his wife Diane 7

       Stewart was convicted of murdering Helen Credit: PA:Press Association 7

       Her body was found in a cesspit with dog Boris Credit: SWNS:South West News Service 7

       Stewart smothered her to death