A man has been jailed for life and ordered to serve at least 29 years in prison for murdering his wife and stepdaughter in an episode of “wanton savagery”.

Christopher Boon, 28, stabbed Laura Mortimer and her daughter Ella Dalby multiple times in the kitchen of their home in Dexter Way, Gloucester, on 28 May.

One of his arms was in plaster at the time, as 10 days earlier he had punched a hole in a wall after Mortimer said she wanted a divorce, telling her “that was meant for your face”.

Bristol crown court heard Mortimer “fought for her life” after being attacked by Boon, with Ella, 11, going downstairs to help her. Mortimer had 18 stab wounds, including 13 to her face and neck; Ella had 24 stab wounds.

The pair had several injuries from where they had tried to protect themselves from Boon’s “unspeakable savagery”, Mrs Justice May said.

“Blood found on Ella’s feet leads to the inference that she must have come in when her mother was already bleeding,” the high court judge told Boon. “She would have witnessed some part of your murderous attack on her mother and tried to stop you before you turned the knife on her.

The judge said Boon had committed the murders in ‘an act of selfish rage and cruelty’. Photograph: Gloucestershire police/PA

“What a brave girl. She and her mother were found lying together, side by side, when they died. Your wanton savagery has blighted the lives of many for ever.”

The judge said Boon had committed the murders in “an act of selfish rage and cruelty”.

Boon, an electrical engineer, had previously been convicted over domestic violence. He was sentenced to nine months in prison, suspended for two years, for assault, battery and criminal damage on a previous partner and her mother in 2010.

Richard Smith QC told the court Boon and Mortimer had been married for five years and Ella lived with them.

On 26 January 2014, Mortimer had run to a neighbours’ house in a “hysterical” state wearing only her underwear and claimed Boon had hit her, Smith said. Police were contacted but Mortimer did not support her husband being prosecuted. “It is clear that this defendant has a temper,” Smith said.

The following year, Boon shouted that one of Mortimer’s friends and her family should “watch their backs” after they told her he had been seen out.

At the beginning of 2018, Boon had an affair and the woman involved contacted Mortimer to inform her. Friends told police that Boon was abusive towards Ella.

On 17 May, Mortimer told a friend she had to leave her home after Boon “went for her” and she said she wanted a divorce. “Boon had then punched a hole in a wall and told Laura: ‘That was meant for your face’,” Smith said.

Ten days later, Mortimer went to the pub with friends. She told them her husband was not happy because she had asked him to leave the house within two weeks. She arrived home at 1.10am and spoke to an aunt on FaceTime at 1.18am.

“Some time in the following three hours, the defendant attacked and killed both his wife and her daughter Ella,” Smith said. “Having heard matters dramatically unfold in the kitchen, Ella got out of her bed and bravely came to the help of her mother.

“Eleven-year-old Ella must have witnessed, in part at least, the murderous attack on her mother before Boon also attacked his stepdaughter. It is clear that it was a sustained and brutal episode of violence in which Laura and Ella suffered multiple stab wounds about their faces and necks.” Both died “rapidly”, Smith said.

The families of Laura Mortimer and Ella Dalby outside Bristol crown court with DC Lennox Shaw of Gloucestershire police. Photograph: Claire Hayhurst/PA

Victim personal statements read to the court spoke of Mortimer’s successful wedding planning business, Sweet Beginnings. Her mother, Hilary Bartholomew, described her as a “wonderful, devoted mother” who had “done brilliantly” with her business.

Ella’s father, Tom Dalby, said: “Every day I feel the terror and pain Ella must have felt in the last moments of her life.” The student at Barnwood Park Arts College was described as having an “outstanding dancing talent”.

More than 1,000 mourners attended their funeral at Gloucester Cathedral.

Representing Boon, Stephen Leslie QC said his client had experienced a “total loss of control” and the murders were not premeditated.

Speaking outside the court, the victims’ families said: “No sentence will ever be enough to pay for what he has done to them and to us. He has given us a full life sentence of loss and sorrow.

“We are thankful that this cruel, brutal monster will spend years behind bars where he can contemplate and comprehend the heartlessness of his actions.”

• In the UK, the domestic violence helpline is 0808 2000 247. In Australia, the national family violence counselling service is on 1800 737 732. In the US, the domestic violence hotline is 1-800-799-SAFE (7233). Other international helplines can be found at www.befrienders.org