Timothy Allen beheaded his wife after X Factor 'puppets' delusion

Her head and body were discovered separately and a post-mortem examination concluded she died of multiple cuts to the neck.

Southwark Crown Court in London heard that the couple, who met at university in 1995, had been watching the ITV talent show on August 29 when Allen suffered a delusion and attempted to take his own life.

Andrew Jackson, prosecuting, said: "They had been, it seems, watching X Factor together on television - that appears to have been the trigger for what happened."

Allen then turned the knives on his wife and also on the couple's pet dog, Cherry.

He later told police he had believed the dancers were "puppets being controlled by a puppet master" and they were "speaking" to him through the television.

He believed this was an attempt to punish him and his wife with "eternal damnation" for an imagined crime and so decided he had to take her life and his own, Mr Jackson added.

"When she asked him not to kill her, he carried on and had meant to do so," he said.

Ms Ho called 999 shortly before 11pm and told police her husband had tried to kill himself.

When officers arrived, they found a bare-chested Allen "in the process, having killed Samantha, of killing their dog".

Allen, of Curlew Place, St Neots, denied murder and prosecutors accepted his guilty plea to manslaughter by diminished responsibility.

Medical reports from four experts suggested he had suffered a catalogue of psychiatric problems, including paranoid schizophrenia, following a serious motorbike accident in 2004.

Bioscientist Ms Ho (pictured below) had been a "caring, loving and supportive partner", Mr Jackson said.

Peter Doyle QC, defending, said Ms Ho was "saintly" and had "never faltered" in her care for her husband.

"Her last act was to ring the emergency services to bring help to him," he said.

Following his accident, Allen had found it hard to keep jobs, unsuccessfully applying for 140.

In the week before the attack he had visited his GP twice and was referred to mental health services before being allowed to return home.

He had never tried to harm his wife prior to the incident.

Sentencing the 40-year-old, Mrs Justice McGowan said Allen presented a risk to the public.

She ordered that he be detained under Section 37 of the Mental Health Act 1983, and made a restriction order under Section 41 of the same Act that he not be released from a secure hospital until the Secretary of State deems him not to be a risk.

The judge said: "This was a terrible offence. You killed the woman that you loved and who I'm completely satisfied also loved you with a selfless commitment.

"This was a happy, loving couple, working well together and successfully until the events of 2004 and the road traffic accident.

"What happened that night was clearly a product of a severe and chronic mental illness. This is one of the sadder cases that this court has had to deal with."

A statement from Ms Ho's family said: "Samantha was a well-loved, well respected, kind-hearted young lady.

"She had a bright future ahead of her with lots of aspirations. She wanted to be a great scientist, have time to travel the world, realise her dreams and spend more time with family.

"We have put our faith in the justice system to make amends for this crime and we welcome today's result. However, no sentence can bring Samantha back.

"However, on that fateful day, August 29 2015, Samantha was tragically taken away from us. That day was a day where a part of us died."

Punam Malhan, senior district crown prosecutor for CPS East of England, said the prosecution considered the medical reports "very carefully" before deciding to accept Allen's plea.

She said: "This is a tragic case where Mr Allen's long-term mental health problems deteriorated to such an extent that he killed his wife in an extremely brutal fashion.

"At the time of the killing we were satisfied on the medical evidence presented to us that Mr Allen was suffering from a mental illness which caused an abnormality of the mind, substantially affecting his ability to behave rationally and keep his self-control.

"Had it not been for that, he would not have killed the wife who loved and cared for him and to whom, on the available evidence, he had never previously threatened any violence.

"We are satisfied that accepting a plea to manslaughter on the grounds of diminished responsibility is the correct course in this case and will allow Mr Allen to receive treatment for his mental illness."