The cell mate of a killer found hanged in jail has been charged with murdering the prisoner.

Alcoholic Gareth Russell died at Lewes Prison on April 24, less than a week after he was found guilty of manslaughter for the killing of street drinker Terry Hannaby in Brighton. He had been sentenced to six years in jail.

Sussex Police launched an investigation into the death of the killer and last night they arrested Russell's cell mate and charged him with the 25-year-old's murder.

Detectives took the man, who officers have refused to name, to a police station in Brighton to question him before accusing him of killing Russell.

Detective Chief Inspector Steve Biglands, of Sussex Police, said: "A male, who is also a prisoner at Lewes Prison, was charged with the murder of a fellow inmate."

The suspect was this morning due to appear before magistrates in Brighton to face the charge.

The Home Office, Prison Service and Lewes prison governor Eoin McLennan-Murray refused to comment on the case.

The Prisons and Probation Ombudsman, which investigates every death in UK prisons, yesterday said it had been unable to start its inquiries because police inquiries were still being carried out.

Russell was found hanging by prison staff just after midnight on April 24.

Staff at the 558-capacity prison tried to revive him and called an ambulance at 12.07am. He was taken to the Royal Sussex County Hospital in Brighton but doctors were unable to save him. He was declared dead just after 1am.

Russell had been found guilty of manslaughter on April 19 after a seven-week trial at Hove Crown Court. He had been living rough in Brighton area for some time. A judge said he had stood "shoulder to shoulder" with Anthony Griffiths, 33, and Andrew Stanley, 40, during the attack on Mr Hannaby, 34, in Bartholomew Square, Brighton, on September 4 last year.

Mr Hannaby's body was found by security staff at Brighton Town Hall. He had been kicked to death.

Stanley and Griffiths, also street drinkers of no fixed abode, were found guilty of murder. They were jailed for life and will have to serve a minimum of 12 years before they are considered for release on licence.

The court was told Mr Russell had suffered brain damage from trauma and alcohol abuse, which could have affected his actions.

Mr Russell was the third Sussex prisoner to die in custody during April. Dafydd Field, 52, who was charged with the murder of his six-year-old son Jethro, was found electrocuted in his cell at Lewes prison on April 10. Emma Kelly, 31, from Heathfield, was found hanging in her cell at Send prison in Surrey on April 18. She was eight months into a nine-year sentence for supplying cocaine and heroin to her son.