Helen Bailey murder: Fiance Ian Stewart found guilty

Stewart and Ms Bailey met online following the deaths of their respective spouses

The fiance of a children's author who drugged and suffocated her before throwing her body in a hidden cesspit has been found guilty of murder.

Ian Stewart, 56, had denied murdering Helen Bailey at their home in Royston, Hertfordshire, in order to get his hands on her near-£4m fortune.

He was convicted at St Albans Crown Court following a seven-week trial.

Police say they will look again at the death of Stewart's wife Diane in 2010 following the verdict.

Mrs Stewart died after having an epileptic seizure in the garden of the family home in Bassingbourn, Cambridgeshire. An inquest was held but police will now re-examine the case.

Helen Bailey: A life shaped by death

Live: Reaction to Ian Stewart guilty verdict

Described by police as "a narcissist" who was "cold" and "calculating", Stewart had "grossly deceived" 51-year-old Ms Bailey when they met online following the death of her husband in 2011.

Prosecutors said he had played "the long game" in order to inherit Ms Bailey's fortune, made from the publication of more than 20 books including the popular Electra Brown teenage fiction series.

Stewart had been secretly giving his fiancee a sleeping drug zopiclone for weeks before he eventually smothered her with a pillow, a pathologist told the jury.

On the day of the murder, 11 April last year, Stewart tried to change a standing order from Ms Bailey's account to the couple's joint account from £600 to £4,000 a month.

He later tried to use power of attorney in order to sell a flat she had in Gateshead.

The author's body was discovered in a cesspit at her home three months after she went missing

He had reported Ms Bailey missing on 15 April and made a heartfelt appeal for his wife-to-be to make contact.

"Whatever has happened, wherever you are I will come and get you," he said.

He told police Ms Bailey had left a note saying she needed "space" and had gone to her holiday home in Broadstairs, Kent.

Her body was found three months later, having been pulled out of a "hard crust" of excrement inside the cesspit underneath the garage of the couple's £1.2m home.

Her pet Dachshund Boris was found alongside her.

The court heard how, in 2013, Ms Bailey had told her brother John the cesspit would be a "good place to hide a body" while giving him a tour of the house and grounds.

Stewart had been with them at the time, the jury was told.

The bodies of Helen Bailey and her dog were found in the pit beneath the garage

The Crown Prosecution Service said Stewart had "conducted a cynical, deceitful and calculated charade as he watched the police conduct a futile missing person investigation".

All along he had denied murdering Ms Bailey, instead claiming two business associates of her late husband had kidnapped her and tried to blackmail him.

He told St Albans Crown Court that the men - Nick and Joe - had told him not to inform police about the kidnapping and had threatened to harm Stewart's two sons.

The prosecution said he was a liar and an actor who talked "bizarre nonsense".

Following the verdicts, Stewart refused to return to the dock while the judge heard mitigation from the defence.

Simon Russell Flint QC, defending, said "there is little I can say" regarding the offences Stewart had been convicted of, and there was every prospect his client would "end his days behind bars"

Judge Bright said he was prepared to sentence Stewart on Thursday morning, and if he refused to leave his cell he would be sentenced "in his absence".

Det Ch Insp Jerome Kent from the Bedfordshire, Cambridgeshire and Hertfordshire Major Crime Unit described Stewart as a "particularly cold and wicked individual".

"There's no doubt in my mind that Helen Bailey loved him with all her heart," he said, "and he is the one person who should have protected her and should have looked after her.

"I don't believe he had any close feelings for Helen Bailey. Certainly the way he disposed of her body is an indication of the way he thought of her."

In a statement, Ms Bailey's family said despite the "victory for justice", there could be "no celebration", and their thoughts were with Stewart's family.

"Our families have been devastated and nothing can ever bring Helen back to us, or truly right this wrong," they said.

"A long shadow of loss has been cast over the lives of so many who will always remember Helen with enduring love and affection."

Ian Stewart's wife Diane died in 2010 after having an epileptic seizure

Det Ch Insp Kent also confirmed his team would be looking again at the death of Diane Stewart in 2010.

He said there was "no indication" of anything untoward, but understood the murder trial verdict opened up further suspicion.

"It's only right that I consider what might have happened in Ian Stewart's past to see whether there's anything I need to get involved in, whether there's any fresh evidence that might have come out from this trial," the detective said.

"That's something we will be doing in hand with the Cambridgeshire Coroner at the end of this investigation."

Stewart was also found guilty of preventing a lawful burial, fraud and three counts of perverting the course of justice.

He will be sentenced on Thursday.