A "cold-blooded" killer strangled his prison cell mate to death while singing the American national anthem, a court heard.

Simon Wishart, who claims to be from the States, throttled Gareth Russell then made out his victim had hanged himself.

After the killing he bragged: "I loved the way it made him feel powerless", a jury was told.

Wishart, 22, formerly from Eastbourne, denies murder at a trial at Lewes Crown Court.

He is accused of killing Mr Russell, 25, who was found dead in cell 19, in the jail's care and support unit for vulnerable prisoners, just after midnight on April 24 last year.

Mr Russell had been convicted of manslaughter days earlier and was beginning a six-year jail sentence.

The court heard when Wishart first raised the alarm he claimed his cellmate had committed suicide and he had found him hanging from heating pipes by a ligature made from torn bed sheets.

But Wishart, who was in jail on remand waiting to go on trial for robbery, allegedly later admitted killing him.

He is alleged to have told a member of the prison staff while he killed his cellmate he started singing the American national anthem because Mr Russell would "wind him up" as Wishart was originally from the US.

Jeremy Gold QC, prosecuting, told the court: "The prosecution case is the defendant deliberately strangled Gareth Russell with a ligature before embarking on a bizarre attempt to make it look like Mr Russell had hanged himself in his cell."

"The murder of Gareth Russell was carefully planned by someone who knew exactly what he wanted to achieve."

Mr Gold said when police investigated the apparent suicide they discovered Wishart and Mr Russell had played games together involved burning each other with cigarette lighters to relieve the boredom of being in jail.

The jury would also hear evidence from other prisoners who claimed Wishart had threatened to kill Mr Russell because he annoyed him.

Days before Mr Russell died, Wishart allegedly asked a fellow prisoner, in jail for strangling his wife, how it felt to kill someone.

The day before the alleged murder, he is accused of telling another prisoner he was going to kill Mr Russell, from Brighton, because his cellmate was annoying him. He allegedly threatened: "I will put a rope around his neck if I have to."

On the day Mr Russell died, Wishart is alleged to have told his girlfriend that his cellmate was getting on his nerves and he threatened to hang him from the window of the cell and after waiting a few hours, he would ring the alarm bell and claim it was suicide.

Hours later, at just after midnight, Wishart rang his cell bell and told the prison officer who answered: "Get me out of here. He has hung himself."

Mr Gold said Mr Russell's body was on the floor and he was clearly dead. A ligature made from strips of bed sheet was around his neck.

Three days later Wishart was arrested and made curious comments to officers guarding him overnight at the police station, including: "Maybe I did do it, maybe I didn't. Maybe I will never know. Before I die I want to be known."

When Wishart returned to jail he was sent to the hospital wing where he allegedly confessed to a member of staff he strangled Mr Russell and tried to make it look like suicide.

He claimed he had killed his cellmate because Mr Russell had sexually touched him when they were tied up during one of the games they played together.

It was then he made the claim about singing the American national anthem.

He allegedly confessed he had whispered in Mr Russell's ear as he throttled him: "I told you I would get you back for that," meaning for the alleged sexual abuse.

He is also alleged to have said: "I loved the way it made him feel powerless."

Mr Gold said Wishart was arrested again and continued to give conflicting accounts of what happened. He had claimed Mr Russell died by accident after they both were seeing how long they could hold their breath while something was tied around their necks.

The members of the jury were told they would have to decide whether the killing was murder or manslaughter due to diminished responsibility.

Mr Gold said: "This was quite simply cold-blooded murder."

The jury were shown DVD footage of the cell, including a picture stuck on the wall allegedly drawn by Wishart depicting a graveyard and people hanging from a tree.

The court heard Mr Russell was in jail after being convicted of manslaughter and had been sentenced to six years in prison. Mr Gold said there were no evidence to show Mr Russell, who had been cleared of murder, was depressed at his conviction. But he had been in the special CAS unit because he had blamed his two co-defendants for the killing, which could have caused ill-feeling.

The trial continues.