An anonymous witness in the Pentonville Prison murder trial has withdrawn after his cover was blown after less than an hour in court.

Islington Gazette: Jamal Mahmoud. Picture: Met PoliceJamal Mahmoud. Picture: Met Police (Image: Archant)

The inmate, known by the pseudonym Bobby Dorset, was giving evidence for the prosecution in the case of three prisoners accused of killing new father Jamal Mahmoud at the Caledonian Road jail.

The 21-year-old was stabbed to death on the landing of G Wing in October last year, allegedly following a power struggle over the smuggling of contraband into the prison.

Special measures were taken in Court 10 of the Old Bailey to ensure Mr Dorset’s true identity was kept a secret.

He spoke through a distorting voice modulator and his face was hidden from view by a screen.

But after less than an hour in the witness box last Wednesday, Judge Richard Marks QC called a halt to his evidence and sent the jury home.

A week later, the jurors were recalled to court and the judge explained that Mr Dorset was unwilling to continue after his true identity was revealed by a “very regrettable” accident.

Judge Marks said: “Ladies and gentlemen, you will recall that last Wednesday, just before lunch, the witness Bobby Dorset began to give evidence and certain special measures had been put in place in relation to the manner in which his evidence was given.

“He resumed his evidence after lunch. After about half an hour, matters were brought to my attention which led to our breaking off from his evidence and it has not been possible to resume the case with you since that time.

“The nature of the problem which arose was that it became apparent that the true identity of the witness Mr Dorset had become known.

“Having looked into the matter in some detail, I am entirely satisfied that this very regrettable situation arose by reason of a genuine accident.

“It was in no way whatsoever the fault of the witness himself or the prosecution or the defence or any of the defendants.

“This development was made known to the witness and the upshot is that he is no longer willing to give any further evidence and so you will not be hearing from him further.”

The judge said Mr Dorset had already given some evidence but had yet to say anything about what he saw on the day of the killing.

He said he would give more directions to the jurors about what they had heard from Mr Dorset whose evidence had not been tested by defence cross-examination.

He added: “Above all else, it is critically important you do not hold it in any way whatsoever against any of the defendants.”

Basana Kimbembi, 35, Joshua Ratner, 27, and Robert Butler, 31, have denied murder and wounding Mr Mahmoud’s associate, Mohammed Ali, with intent to cause him grievous bodily harm.

The trial continues.

Reporting by Press Asssociation