A double murderer who carried out the “bloodthirsty” killing of a woman and dumped her dismembered body has been jailed for the rest of his life.

Builder Steve Sansom was out of prison on life licence when he killed Sarah Mayhew, 38, and disposed of her remains in different locations around London, the Old Bailey heard.

The 45-year-old, who murdered a taxi driver in 1998, and his partner Gemma Watts both admitted murder and also perverting the course of justice by dismembering Ms Mayhew’s body.

Mrs Justice Cutts sentenced Samson to a whole-life order, which means he will never be released from prison. Watts, 49, was sentenced to life imprisonment with a minimum term of 30 years.

Sentencing the pair, Mrs Justice Cutts said Ms Mayhew’s “greatest misfortune was to know the two of you”.

Warning: The following story contains distressing details

Ms Mayhew had two children, who were aged 12 and 15 when she was killed.

She had met Sansom, from Sutton, on a dating website a few years before.

The judge said she was “quite certain” that graphic messages of sexual violence between Sansom and Watts moved from fantasy to a plan to involve a third party, whom they planned to murder.

When Sansom contacted Ms Mayhew “he had murder in mind” and she had been taken to his flat for “depraved and violent sexual activity”, the court heard.

“Her fear and suffering must have been acute as she realised why she was there and what was happening,” Mrs Justice Cutts added.

“She was an innocent woman lured to that flat to die,” she said, so the pair could act out their “bloodthirsty and wicked fantasy”.

The court heard Sansom had never shown remorse for what he had done.

The judge said she was in no doubt his offending was exceptionally high and that it required a whole-life order.

Watts was “obsessed” with Sansom, but it was not a case of “one person’s will being overborne by another”, the judge said.

Prior to sentencing, in a statement read to the court, Ms Mayhew’s father, David Mayhew, said: “I ask myself the same question all the time: ‘Why did you have to kill her?’ Maybe I will never know.”

He thanked the killers for pleading guilty to murder and sparing the family the ordeal of having to go through a trial.

“That said, whatever sentence you receive will never compare to the pain you have caused us,” he said.

Ms Mayhew’s mother, Angela, said she missed her “beautiful, pretty girl”.

“It breaks my heart she is not around, I miss Sarah all the time,” she said.

She added that her daughter was a “popular girl with lots of friends from when she was little” and that she was “really clever at school”.

Before the murder, the killers exchanged “depraved” messages detailing a desire to kill people with a knife or knives while engaged in sexual activity.

Prosecutor Tom Little KC previously told court it was a killing that involved sexual and “sadistic” conduct.

Ms Mayhew had accompanied Sansom to his flat in Burnell Road, Sutton, at about 23:00 GMT on 8 March 2024.

“From that point in time she was never seen again and she never left that property alive,” said Mr Little.

“How long she lived for only the defendants know and they have never said.

“What precisely happened to her body after she had been murdered by them in the property only the defendants know.”

Ms Mayhew’s head and limbs were found more than eight miles (nearly 13km) away in Rowdown Field in New Addington on 2 April, the court heard.

Her torso was discovered later in the River Wandle.

She had been living at Friars Wood in Croydon at the time of her death and knew both Sansom and Watts, who was also from Croydon, Mr Little said.

Messages between the killers indicated that Ms Mayhew introduced them to each other in the summer of 2023.

By the time of the murder, Sansom and Watts had been in a sexual relationship for seven months.

“Messages indicate that from the early stages their relationship was characterised by sado-masochistic violence,” said Mr Little.

“Such was the intensity of the defendants’ relationship at this early stage that they referred to dying together if they were ever caught.”

He added that “given the messages sent between the defendants” it was not possible to conclude Ms Mayhew was killed immediately.

After the murder, Sansom said: “We’re not evil, we’re not evil. We done the world a service.”

The court heard Sansom had murdered before – having served nearly 20 years in prison for stabbing a minicab driver on Christmas Eve in 1998 and stealing his wallet. He was released on licence in 2019.

Charlotte Newell KC said in mitigation that Watts had a history of mental health crises and had been “manipulated” by Sansom.

Both defendants were given concurrent sentences of five years for perverting the course of justice.

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