A “callous” dissident republican who killed an off-duty prison officer in pursuit of a “twisted” ideology should serve at least 22 years in prison, a judge has said.

Christopher Robinson, 50, played an “intimate and inextricable” role in the death of devoted family man Adrian Ismay, Mr Justice Gerry McAlinden said.

He knew him as a fellow St John’s Ambulance volunteer yet chose him for targeting.

The married father-of-three aged 52 died 11 days after suffering serious leg injuries when a Semtex bomb exploded underneath his van shortly after he had driven away from his east Belfast home in 2016.

At Belfast Crown Court, Mr Justice McAlinden said: “His murder was perpetrated in pursuance of a twisted republican terrorist ideology.

“The defendant played an important and integral role in planning and carrying out the terrorist operation which resulted in the death of Mr Ismay.”

He drove the vehicle on the night of the attack to transport another person involved across Belfast before and afterward.

Robinson, from Aspen Walk in West Belfast, has been given a life sentence for the murder but will be eligible to apply for release under licence after 22 years, the judge said.

The extremist group that styles itself as the “New IRA” claimed to have carried out the attack on the long-serving officer.

The judge said: “Such callous disregard for the lives of others in such an attack is actually an aggravating factor.”

Mr Ismay was released from hospital after the blast on March 4 and had been making good progress, but he died unexpectedly less than two weeks later when a blood clot linked to the bombing triggered a heart attack.

He had worked at Hydebank Wood Young Offenders’ Centre in south Belfast, where he trained new recruits to the Prison Service.

He was a St John Ambulance volunteer and deeply committed to all parts of the community, the judge said.

He added: “He was a decent, warm, generous, loving human being and our society is the poorer for his loss.

“If only there were more like him.”

The judge said Robinson searched for information on the internet about the magnetic permeability of aluminium before the device was attached to the van.

Damage to the van being driven by Adrian Ismay after a Semtex bomb exploded underneath it
Damage to the van being driven by Adrian Ismay after a Semtex bomb exploded underneath it (PSNI/PA)

He was intimately involved in targeting him over a lengthy period of time.

The defendant checked his target’s online profile as well as the opening times of a supermarket near where he lived.

Afterwards he took significant steps to cover his tracks, including destroying phone evidence.

His family has been left bereft.

The killer has displayed not a scintilla of remorse, the judge said, and was expressionless during sentencing.

He added: “Only the coldest of hearts of stone would not be affected reading them and anyone of normal sensitivity could not but readily perceive how each of the authors of these statements and those referred to therein have been utterly devastated by this matter and their lives altered irretrievably.

“These statements, with quiet dignity, bring home to me the damage Mr Ismay’s death has caused to their lives.”

Mr Justice McAlinden added that prison officers and police officers have been regularly targeted at home and off duty simply because in those environments they are deemed to be easier targets.

Christopher Robinson court case
PSNI Detective Superintendent Richard Campbell (Peter Morrison/PA)

Police Service of Northern Ireland (PSNI) Detective Superintendent Richard Campbell said it was a “cowardly” attack on someone the killer knew.

“Think about the callousness of that,” he said.

“Someone you knew within the society, someone you knew volunteering within the community and to choose that person to kill them is just reprehensible.”