The professor who analysed the brain tissue of Diane Stewart has said at the murder trial of her husband that she suffered a lack of oxygen for up to an hour.

Convicted murderer Ian Stewart - who is 61 and originally from Letchworth - stands accused of killing Diane in 2010 at their Bassingbourn home. At the time was recorded at the time as sudden unexplained death in epilepsy (SUDEP).

Police launched an investigation into Diane's death after Stewart was found guilty in 2017 of murdering his fiancée, Ms Bailey the year before, and dumping her body and her dog Boris in a cesspit beneath the home they shared.

Professor Safa Al-Sarraj, a consultant neuropathologist, was asked to examine preserved parts of Mrs Stewart's brain - which she had donated to medical science.

In court on Monday, Prof Al-Sarraj said he observed "changes in the brain... consistent with early ischemia". He defined ischemia as "damage to the cells due to lack of oxygen and blood supply" and he estimated the damage happened over 35 minutes to an hour but conceded he was a "bit reluctant" to give figures "as they are all estimates".

Prosecutor Stuart Trimmer QC asked Prof Al-Sarraj: "(With a) healthy breathing human you don't expect to find any evidence of ischemia, do you?" Prof Al-Sarraj said: "No."

He said ischemia may be found in cases where a person dies after suffering from "restricted" breathing for "30 minutes plus", but said: "You may have look carefully for it."

Amjad Malik QC, defending, said: "SUDEP is possible as the cause of death for Diane Stewart, isn't it?"

Prof Al-Sarraj replied: "I agree. Yes, it's one of the things you have to consider - but it's not the only cause of death you had to consider."

A second expert witness, consultant neuropathologist Dr Kieren Allinson, said there was "no positive evidence of a recent seizure", such as tongue biting.

He described epilepsy as "awful" and said "people die suddenly and unexpectedly of the disease".

Dr Allinson agreed with Mr Malik that the absence of evidence of a seizure "doesn't make it unlikely that SUDEP occurred".

He said: "A history of recent seizure is a risk factor for SUDEP but often they haven't had a seizure for many years."

The trial continues.