Warning: This story contains distressing details

A mum and her new boyfriend have been jailed for life for the “sadistic” abuse and murder of her two-year-old daughter.

Isabelle Welsh was a “happy and thriving” child before her mother, Alexandra Walker, invited Harrison Simpson into their lives in Thornaby, Stockton, in June 2025, Teesside Crown Court heard.

A judge said Isabelle was the victim of a campaign of violent and sexual abuse at the hands of those meant to love, care for and protect her.

Simpson, 22, and Walker, 26, were both found guilty of murder and child cruelty, with Simpson also convicted of sexual abuse of a child. Simpson must serve a minimum of 28 and a half years and Walker 22 years.

Ms Justice Norton said both were “equally and jointly responsible” for Isabelle’s murder and the campaign of cruelty she endured, with the couple putting up a “wall of silence, lies and obfuscation” about the last weeks of her life.

The court heard Isabelle was fatally injured at her home on the morning of 13 September 2025, with Walker not calling 999 until hours later.

The judge said Isabelle had either hit her head against a hard surface when she was violently shaken, or her killer swung or flung her by the legs into a wall or piece of furniture.

The two-year-old instantly suffered a fractured skull and an “unsurvivable” brain injury, with her condition immediately and obviously deteriorating, the judge said.

It could not be said who inflicted the fatal injury, the court heard, but Walker claimed she was sleeping in after a drink and drugs binge at the time and only found Isabelle injured in her cot later.

The judge said “silent” Simpson never gave any account for what happened, while Walker was a “fantasist and attention-seeker” who “told lies from start to finish”.

Instead of calling for help as soon as she found her “dying child”, Walker waited for at least an hour, in which time she put Isabelle on the floor, cleared away evidence of the couple’s cannabis use and went outside to smoke, the court heard.

“I have no doubt your lack of urgency or concern was because you wrongly believed she was already dead and you were working out what to do to save your own skin,” the judge told Walker.

Norton said Walker’s concern at every step had been to look after her own interests and “never Isabelle’s”.

The killing was the end of a “series of assaults” which the couple had covered up, the judge said, during which time Isabelle must have been in “significant pain and increasing fear of the violence escalating”.

The couple delayed getting medical help for Isabelle as long as they could, and when she did take her, Walker lied repeatedly to clinicians, the court heard.

Tragically, the judge said, when some medical staff wanted to start safeguarding procedures, which “may have saved Isabelle’s life”, they were “overruled” by other doctors who accepted Walker’s “false account”.

The judge said it was “incontrovertible” that Isabelle was a “happy, healthy and thriving child” before Simpson came into her life, but “within a matter of weeks” she was being physically and sexually abused.

Norton said Walker had looked after Isabelle “appropriately” before June 2025, telling her: “In your own way I’m sure you loved her, but you were more interested in yourself and your needs than you were in Isabelle’s.”

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