A 21-year-old man who pushed his grandfather down the stairs in a brutal attack which left the victim with life changing injuries has been sentenced to 19 years in prison.

Jack Sibley, of Jessop Road in Stevenage, was found guilty of assault with intent, conspiracy to rob and perverting the course of justice on Friday after attacking his grandfather Barry Sibley.

The grandson’s friend Warren Reid, 22, of Seaton Road in Luton, was found guilty of the same crimes and jailed for 19 years and nine months.

The attack took place at around 12.30am on May 13 last year in Penton Drive, Cheshunt.

Mr Sibley, who was 82 at the time, was woken in the night by intruders.

Armed with a decorative knife, he went out to the landing to investigate and was set upon by two men who disarmed him, pushed him down the stairs and assaulted him with the knife – later found dumped in Great Wymondley.

The two men then fled to Stevenage empty handed.

A neighbour heard Mr Sibley calling for help and went to assist. He found the victim at the foot of the stairs with serious injuries and called the emergency services.

The attack left the victim with multiple cuts to his scalp and face, a stab wound to the chest and the loss of a finger.

He almost lost a second finger, and had a dislocated shoulder and facial fractures.

Sibley’s mother, Lorraine, also of Jessop Road, was found guilty of perverting the course of justice. The 48-year-old attempted to cover for her son and said the injuries were sustained after he fell on broken glass at their home.

She received 12 months for perverting the course of justice.

Det Sgt Jon Leak, part of Herts police’s Operation Manhunt team which investigated the crime, said: “The victim’s injuries show a brutal and sustained attack on him. He has been left with life changing injuries but more importantly the psychological trauma of the events will stay with him for life.

“At the time of the offence Mr Sibley had no idea who the two offenders were and was shocked to learn of their identity.

“This case has been particularly shocking, not only because of the pre-planning, but also the sheer viciousness of the attack on his own family member and leaving him for dead.”

“I’d reassure people that these types of incidents do not happen very often in Hertfordshire.I am pleased with these convictions and the sentences reflect the gravity of the actions of the two men that day.

“Without a doubt these great results were achieved due to the strong evidence gathered by detectives in Operation Manhunt in the planning, execution and aftermath of the offence.”