Prime Minister David Cameron paid tribute to murdered Northern Ireland prison officer David Black yesterday and insisted that his killers would be brought to justice.
The Prime Minister offered his condolences to the friends and family of Mr Black, who died when his car was ambushed by dissidents.
"First and foremost, this is a dreadful tragedy for the family and friends of David Black, who has been so brutally murdered as he went about his work keeping the people of Northern Ireland safe. My heart goes out to them," Mr Cameron said.
"The Government I lead will do whatever we can to help the PSNI bring the perpetrators to justice.
"These killers will not succeed in denying the people of Northern Ireland the peaceful, shared future they so desperately want."
Mr Black, from Cookstown, Co Tyrone, had more than 30 years' experience in the Prison Service and was approaching retirement.
He was ambushed by a gunman on Northern Ireland's M1 motorway early this morning as he drove to work at the top-security Maghaberry jail near Lisburn, Co Antrim.
Politicians on all sides have condemned the murder and, even though no organisation has admitted responsibility, security chiefs believe republicans opposed to the peace process were involved.
The extremists have been involved in long-running protests against conditions inside Maghaberry.