A widower who shot dead his daughter’s ex-partner and her ex-partner’s father over a family court case involving his grandson has been sentenced to life in prison with a minimum term of 25 years.

Stephen Alderton, 67, had written in previous text messages that he would “override any court decision” and that there was “always a plan B”, Cambridge Crown Court heard.

Prosecutor Peter Gair said former chartered quantity surveyor Alderton shot the two men with his Beretta shotgun on March 29 this year, two days after a family court hearing.

The Hunts Post: Stephen Alderton has admitted shooting dead father and son Gary and Josh Dunmore on March 29.Stephen Alderton has admitted shooting dead father and son Gary and Josh Dunmore on March 29. (Image: POLICE)

The defendant, of no fixed address, pleaded guilty at an earlier hearing to the murders of Joshua Dunmore, 32, and his 57-year-old father Gary Dunmore.

Judge Mark Bishop described the murders as an “execution” and told the defendant, who wore a silver crucifix necklace in court: “You took the decision to take the law into your own hands and end the lives of two innocent men.”

He said Alderton did this over his “distorted beliefs” about family court proceedings involving his grandson “following what was an interim and not final hearing on March 27”.

The Hunts Post: The bag of pellets found in Alderton's motorhome and the pellets used in the murders.The bag of pellets found in Alderton's motorhome and the pellets used in the murders. (Image: Cambridgeshire Constabulary)As he was led to the cells a family member of the two dead men, who was in court, swore and shouted “rot in prison”, which was followed by brief applause.

Joshua and Gary Dunmore were found dead at their homes in villages six miles apart in Cambridgeshire, with Joshua’s home in Bluntisham and his father’s in Sutton.

After Alderton was arrested hours later by armed officers on a motorway, he told police that “sometimes you have to do what you have to do even if it’s wrong in the eyes of the law”, Mr Gair said.

“We say it’s clear that the events were triggered by an ongoing family court case between this defendant’s daughter Samantha Stephen, nee Alderton, and her former partner Joshua Dunmore,” he said.

“This concerned a request to move their seven-year-old child from the jurisdiction of the court by emigrating to the USA.”

He said that Mrs Stephen and Mr Dunmore’s relationship ended shortly after their son was born and in 2020 she married her current partner, Paul Stephen.

Mr Gair said Mr Stephen, a US national, served with the US Air Force.

“He was due to be redeployed back to the USA,” said Mr Gair.

He said they “sought permission of the family court and Joshua opposed the application”.

“There was a hearing on March 27 2023 and it would appear (the child) wouldn’t be removed from the jurisdiction,” said Mr Gair.

Adrian Langdale KC, mitigating for Alderton, said Alderton’s wife died in December 2019.

Mr Gair said Alderton sold his home and was living at the time of the offences in a motorhome on a site in Willingham, Cambridgeshire.

Mr Gair said that Alderton was “rapidly identified” as a suspect after the shootings due to the family court case and sightings of the white Peugeot.

His motorhome was picked up by police using ANPR (automatic number plate recognition) cameras.

He was stopped by armed police from the West Mercia force on the M5 near Worcester at about 1.30am on March 30, police said.

Bodycam footage has since been released of Alderton's arrest.

Mr Langdale said the defendant wrote in a letter: “I’m not the person that this conflict and the family courts have driven me to become.

“I’ve never been a violent person, I do not have a criminal record.

“I’ve been a respectable, law-abiding citizen all my life.

“What happened to me on March 29 I do not know.”

Following Alderton's sentencing, loved ones of Gary and Joshua Dunmore made no comment as they left Cambridge Crown Court. 

DCI Katie Dounias, from Cambridgeshire Police's major crime unit, said: “On March 29, Stephen Alderton turned a family dispute playing itself out through the courts into a double tragedy by his rash and brutal actions.

“Our thoughts are with the family and friends of Gary and Josh at this difficult time. There is no sentence sufficient to heal the trauma they have endured but I hope today’s sentencing will provide some solace.”