A 21-year-old inmate was killed at Pentonville Prison in a bloody battle to control the wing’s “lucrative” contraband route, a court heard.

Islington Gazette: A general view of Pentonville Prison. Picture: Anthony Devlin/PAA general view of Pentonville Prison. Picture: Anthony Devlin/PA (Image: PA Archive/PA Images)

Basana Kimbembi, 35, Joshua Ratner, 27, and Robert Butler, 31, allegedly murdered new father Jamal Mahmoud, at the Caledonian Road jail on October 18 last year.

Opening their Old Bailey trial today, prosecutor Mark Heywood QC described how Mr Mahmoud was attacked with such “calculated brutality” that it shocked even hardened prisoners.

He said: “He was killed by a group of men armed with weapons that went to find him and those with him. That lethal violence was quite deliberate and expected.

“When it happened, both sides knew that it was going to happen and were prepared to engage in it. In the event, the level of it was shocking, shocking to those who lived in that place.

“The second most shocking aspect of this death is that it took place in one of Her Majesty’s prisons, on a wing populated with people who had been there for some time, overseen 24 hours a day by regular staff.

“The sheer determination of the killers is indicated by the fact that neither the location, the security or the presence of prison staff served to stop it or deter the violence or the weapons used to drive it home.

“The Crown’s case is that these three defendants together armed themselves in advance and went to confront Jamal Mahmoud and his group who also were armed.

“They did so to make their point and to succeed in resisting the others and getting control of part of the lucrative contraband route onto that wing of the prison.

“In doing so, they acted together, intending to use the weapons to cause really serious, even lethal harm: to confront.”

Islington Gazette: A general view of Pentonville Prison. Picture: Charlotte Ball/PAA general view of Pentonville Prison. Picture: Charlotte Ball/PA (Image: PA Wire/PA Images)

The defendants have denied murder as well as wounding a second man, Mohammed Ali, with intent to cause him grievous bodily harm.

On the day of the attack, there were 1,271 inmates, of which 376 were on G Wing, jurors heard.

Married Mr Mahmoud, nicknamed Chaos or K, had celebrated the birth of a son in January last year.

He was part of a group on the Wing known as The Somalis, which included Mr Ali, whose prison tag was Jimmy.

The pair had occupied key cells on G Wing – G502 and G503 – from which they had power over the influx of phones, weapons and drugs as they were delivered by drone or other methods.

Mr Heywood said: “In the circumstances here there was a very good reason why somebody wanted cells where the dead man was housed.”

By mid-October last year, a “serious dispute” had developed over this access, the court heard.

One of the defendants was to later tell prison authorities that Mr Mahmood was “playing with the big boys”.

The day before the killing, a package had come into the prison and there was open talk of a “beef”, jurors heard.

Islington Gazette: A general view of Pentonville Prison. Picture: Anthony Devlin/PAA general view of Pentonville Prison. Picture: Anthony Devlin/PA (Image: PA Wire/Press Association Images)

A civilian employee saw a length of sheet dropped from the fifth floor window over the prison wall into the street before it was pulled back, jurors heard. It was clear weapons were on the wing, jurors were told.

The victim was seen by another inmate to visit Butler and Kimbembi in a cell.

During their discussion, Kimbembi allegedly pulled a large combat knife from a sheath and told him to move back.

Mr Mahmoud left, saying “we’ll see what happens” and Kimbembi allegedly looked up and said “I am going to kill you”.

Mr Heywood said: “Whatever he meant by those words, the fact is he did. He did so within about 24 hours.”

Jurors were shown pictures and given a virtual tour of the prison, although the prosecutor said they would get the opportunity to see it “in reality” later on.

Mr Heywood said that since the killing there had been changes to security at the five-floor block, in which the victim was housed in a top floor cell.

On the evening before his death, Mr Mahmoud called his wife and told her about the trouble over the parcel containing phones, SIM cards and a knife, the court heard.

He told her he was irritated because it was “his operation”. He described the confrontation, allegedly with Butler and Kimbembi, and said he had arranged for someone to steal the parcel.

Islington Gazette: A general view of Pentonville Prison. Picture: Anthony Devlin/PAA general view of Pentonville Prison. Picture: Anthony Devlin/PA (Image: PA Wire/PA Images)

On the day of the killing, Mr Mahmoud told his wife he still felt “violated” having been threatened with a knife and she told him not to do anything stupid, jurors heard.

He also told another inmate that he had confronted the men and told them: “If you want war, I will give you war.”

The inmate allegedly approached a prison officer and warned not to open the defendants’ cells or there would be trouble.

Supervising officer Dizzy Vergo spoke to the defendants and allegedly told them they may be victims of something but let them out after they gave her assurances.

Shortly before the killing, Kimbembi was overheard by another inmate, Bobby Dorset, to tell the victim: “I was gonna come up and see you this afternoon.”

Mr Mahmoud allegedly replied: “It has gone past talking now.”

The trial continues.

Reporting by Press Association

Islington Gazette: A general view of Pentonville Prison. Picture: Charlotte Ball/PAA general view of Pentonville Prison. Picture: Charlotte Ball/PA (Image: PA Wire/PA Images)