A prisoner serving a life sentence for murdering his girlfriend in Homerton had his time behind bars extended by two years after knocking a guard unconscious.

Douglas Samuel was jailed in 2013 for a minimum of 20 years for murdering his partner Gaynor Bale a year previously. He had regularly subjected her to violence at her flat in Homerton, London.

His sentence was reduced to 18 years by the Court of Appeal in 2014.

Samuel, now 41, was a prisoner at Whitemoor in Cambridgeshire at the time of the new offence. He became violent and confrontational after he was kept waiting to see a prison doctor on November 13 last year.

He started causing problems on the prison wing at around 3.30pm and remained at the centre gate, refusing to move away and allow prison officers to continue their work.

Samuel was approached by two prison officers and was ordered to go back to his cell, but he refused and became verbally abusive.

He shouted to other prisoners on the wing to come and help him. The two prison officers then began to escort him along the landing and back to his cell but as they did so, Samuel elbowed one of them in the face.

The force of the blow caused the officer to fall backwards and hit his head on the concrete floor, knocking him unconscious.

After the attack Samuel ran back to his cell. The prison officer was taken to hospital and suffered a fractured skull and a bleed on the brain as a result of the assault. He suffered no lasting injuries.

Samuel admitted causing grievous bodily harm (GBH) without intent at Cambridge Crown Court yesterday (August 6).

He was sentenced to an additional two years in prison for the offence and will now serve his original prison sentence of 20 years in full before being eligible for release.

DC Shelly Reeve, who investigated, said: "Samuel had already proved he was extremely dangerous when he was convicted of murdering his partner.

"He was sent to a category A prison, where the most serious offenders are kept, and as a result of his actions he will be staying behind bars a little while longer."

A statement from the victim's parents, read out in court at the time of his appeal, said: "What gave you the right to hit our daughter?

"You are a nasty bully who has taken our daughter away."

Samuel's lawyers had launched a bid to challenge his murder conviction, arguing the judge misdirected the jury in relation to the previous attacks.

But this was rejected by the Appeal Court judges, who said the conviction was safe.

However, the court did alter his sentence, saying his tariff was too long in light of the fact he did not intend to kill Ms Bale.

Judge Michael Stokes QC said: "No-one should leave this court with the view that we do not regard this as a very serious case of domestic violence.

"If there had been a stabbing or the like involved, we would not have altered the sentence.

"In this case however, the appellant accepted throughout the trial that he was responsible for the fatal injury, and the judge accepted he had no intention to kill."