A double killer was jailed for four years and eight months today after savagely slashing a fellow prisoner in a jail attack.

Convicted murderer David Collins, who was locked up for dismembering one of his victims at a Renfrewshire flat, launched the assault on John Rocks at Addiewell Prison, in West Lothian.

At the High Court in Edinburgh, judge Lady Carmichael told 48-year-old Collins that he had participated in "a toxic culture of violence" while behind bars.

She ordered him to start his latest jail term at the end of a 22-year minimum period imposed as part of his life sentence for murder.

Lady Carmichael told Collins: "Your record is one of exceptionally serious violent offending, involving the taking of life on two occasions."

Mr Rocks was having his hair cut by another prisoner on October 29 last year when Collins walked past and, without breaking stride, sliced into the right side of his face with a weapon he had concealed in his hand.

Advocate depute Mark McGuire told the court: "As Mr Rocks reacted and moved away, the accused briefly began to run but slowed to walking at his previous pace almost immediately.

"He walked calmly away from the scene, along the hall, up to the stairs at the end of the hall and into his cell."

The attack was captured on CCTV and, when a prison officer confronted Collins, he responded: "It is what it is."

The victim grabbed a towel and held it to his face as he fled to his cell. He refused to co-operate with a police investigation but underwent surgery to repair nerve damage and had a 16cm wound to his right cheek closed with stitches.

The weapon used in the attack was never recovered, the court heard.

Lady Carmichael was told that Collins was earlier stabbed in Addiewell Prison but claimed to staff that he had fallen.

Following his attack on Mr Rocks, he was transferred to another prison but ended up being scalded with boiling water by a fellow inmate.

Defence counsel John McElroy said the attack in Addiewell was committed after Collins was subjected to bullying.

Mr McElroy added: "He regrets his actions, he regrets his involvement."

Collins, who is now locked up in Grampian Prison, followed proceedings by a video link and admitted assaulting Mr Rocks to his severe injury and permanent disfigurement by striking him on the head with a bladed article.

He was previously jailed for five years for killing his father, also David, with a sword in 2002, after the Crown accepted his guilty plea to culpable homicide under provocation.

Collins was then sentenced to life last year for murdering Kevin Bishop, who suffered a horrific death at his Paisley home in July 2018.

The Gazette: Kevin BishopKevin Bishop

Mr Bishop, 32, was attacked with a machete by Collins, who cut off his head and dismembered his body.

Collins was originally ordered to serve at least 26 years for the brutal murder but his minimum term was reduced on appeal.

He has amassed 30 previous convictions for a total of 67 separate offences, including seven for violence, 15 for disorderly conduct and two for carrying weapons.