Ian Stewart has been found guilty of the murder of his wife Diane in Bassingbourn, six years before he killed fiancée Helen Bailey at their Royston home.

The 47-year-old’s cause of death in 2010 was recorded at the time as sudden death in epilepsy (SUDEP).

Police investigated the case after Stewart, 61, was convicted of the 2016 murder of children’s author Helen Bailey, whose body was found in the cesspit of their home in Baldock Road.

Stewart was found guilty of Ms Bailey’s murder at St Albans Crown Court in 2017.

Stewart told his trial at Huntingdon Crown Court that he found his wife 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.

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.

Royston Crow: The Crow's front page on February 23, 2017, after Ian Stewart was found guilty of the murder of Helen Bailey - he has now been convicted of the murder of his wife Diane.The Crow's front page on February 23, 2017, after Ian Stewart was found guilty of the murder of Helen Bailey - he has now been convicted of the murder of his wife Diane. (Image: Archant)

Stewart was sentenced to 34 years in prison for Ms Bailey's murder. He is due to be sentenced for the murder of Diane.