A primary school teacher arrested in Cumbria for murder has been jailed for life with a minimum term of 20 years for stabbing her partner to death before burying his body in the garden of their home.

Fiona Beal, 50, admitted the murder of 42-year-old Nicholas Billingham, whose partly mummified remains were discovered four-and-a-half months after he was last seen on November 1, 2021.

She pleaded guilty in April during a retrial at the Old Bailey, after her earlier trial at Northampton Crown Court collapsed on its 64th day.

At the end of a two-day hearing on Thursday, Judge Mark Lucraft KC handed Beal a life sentence and told her: "Having moved and buried the body in the garden, you then lied to his mother, numerous friends, all his family and yours as to what you had done and where he was."

The defendant had her head down as she left court.

Outside court after the hearing, a statement by Mr Billingham's mother, Yvonne Valentine, was read out in which she said: "(Beal) has demonstrated extraordinary evil.

"Behind her facade as a kindly school teacher, she was secretly planning the cold-blooded killing of Nick.

"Once the deed was done, she went to great lengths to conceal his body, dumping him in an impromptu grave like rubbish before carrying on with her life as if nothing had happened."

She also referenced having a Christmas drink with Beal on December 23 2021, not knowing she was just feet from her son's body.

"Imagine how, on reflection, the revulsion one felt ... when invited for a drink at her home, devoid of emotion, Beal simply sat looking at me, the mother of the man whose discarded body she had singlehandedly buried just feet away."

The judge, in his sentencing remarks, described it as a "callous act" on Beal's part, "dressed up as a casual chat and a drink before Christmas".

He added: "There was lie after lie."

The mother described Beal as "pure evil" and a "monster".

Ms Valentine held up a photo of her son as her statement was read out by family liaison officer detective constable Kim McHugh.

During the sentencing hearing, prosecutor Hugh Davies KC read out a letter Mr Billingham had written to Beal after he had an affair during their 17-year relationship.

In the letter, Mr Billingham accepted his faults and described Beal as "the most beautiful woman in the world" before promising to never "belittle" her again and declaring he loved her "with all my heart".

On the day of his death, Mr Billingham had worked on a house renovation before returning to the home he shared with Beal in Northampton.

That evening, she killed him in a "carefully planned domestic execution", Mr Davies said.

Beal stabbed him in the neck and disposed of the body in the side return of their home like "building waste", Mr Davies said.

She covered her tracks with a false story that they had Covid and needed to isolate.

Similar messages were sent from Mr Billingham's phone from November 2 in which Beal pretended to be him.

On November 8, Beal sent messages to her sisters saying she and Mr Billingham had split up, with one message saying he left because he had had an affair with another woman.

On her return to work, she received sympathy from those who had heard about the apparent break-up.

Beal's mental health started to deteriorate in late February 2022, the court was told.

In a journal entry dated February 12, she wrote: "I'm not a total monster. I know what I did."

The following month, she rented a cabin in Cumbria and sent messages to family members which gave them cause for concern over her wellbeing, prompting them to call police to check on her.

In the cabin, police found Beal's journals containing a confession to the killing.

They also included reference to her having a split personality and an alter ego she called Tulip 22.

She wrote: "I had smoked all day. I had a bath, I left the water in. He had been pushing for sex. I encouraged the bath with the incentive of sex afterwards.

"While he was in the bath I kept the knife in my dressing gown pocket and then I had it in the drawer next to the bed.

"I brought a chisel, bin bag and cable ties up too. I got him to wear an eye mask."

She went on: "My last words to him when he asked why was that he was not going to do to (another female) what he had done to me."

The journals triggered a police investigation, which soon established Mr Billingham had not been seen or spoken to by telephone since the afternoon of November 1 2021, the court heard.

Beal was arrested in March 2022 after police discovered his body.

Police had visited her home on March 16 but found nothing out of the ordinary.

The next day, officers found a bloodstained mattress in the basement and returned on March 19 and discovered more.

Mr Billingham's mummified body had been buried in makeshift layers of sheeting and concrete.

The murder and cover-up were committed while she continued "to deliver high-quality teaching to Year 6 pupils as if nothing had happened", Mr Davies said.

Andrew Wheeler KC, defending, told the court Beal "had the courage" to plead guilty to the murder after a change in evidential circumstances.

He said the background of Mr Billingham's behaviour towards Beal was "relevant" to the murder and there were a series of events which led to "something never contemplated" - the attack.

After the sentencing, detective sergeant Spencer Bailey, the deputy senior investigating officer in the case, described Mr Billingham as a hardworking man who died at the "merciless hands" of Beal.

"Eventually, all the pressures of her guilt overwhelmed her," he said. "The journal, outlining what the jury was told was her chilling execution of Nick, meant there was never any doubt she had killed him."

Andrew Baxter, from the Crown Prosecution Service. said: "(Beal) exploited a narrative that she was the victim of abuse at the hands of her long-term partner, but rather than leave the relationship, she killed him in a planned, cold-blooded execution when he thought he was safe with his partner."

The original trial collapsed last June when it emerged a key defence witness was a court custody officer who had conducted welfare checks on Beal in the cells.