The jury in the trial of a man accused of murdering his best friend on Christmas Eve has retired to consider its verdicts.

Dylan Thomas, 24, is accused of repeatedly stabbing William Bush, 23, in a “frenzied attack” on December 24 last year at their home in Llandaff, Cardiff.

Thomas has admitted manslaughter by diminished responsibility but denies murder.

Mr Bush and Thomas had been friends since they were about 13, having met at Christ College Brecon, a private boarding and day school in mid-Wales.

Thomas was described to the jury as being “something of a loner” while Mr Bush was more outgoing and active. His brother called him a “loyal” friend.

Mr Bush sustained 37 stab wounds in the attack, including 16 to the neck, while Thomas had cuts to the palms of his hands, which he told police he received while trying to defend himself.

Thomas appeared before Cardiff Crown Court on Thursday by video link from Ashworth Hospital Liverpool, where he is in custody and being treated for schizophrenia.

During the trial, the jury heard from Dr Panchu Xavier, a consultant forensic psychiatrist at Ashworth, who said the defendant could have been having a psychotic episode during the attack and for “up to six months before the event”.

The jury also heard Thomas had been arrested for breaking into Buckingham Palace a few months before the attack on Mr Bush.

Thomas told officers he was looking for “energy fields” between the palace and Cleopatra’s Needle, an obelisk in central London.

He was rugby-tackled by an officer after he told them he was “over now so you may as well show me round”.

Sending the jury out on Thursday, judge Mrs Justice Steyn KC said they may take as long as they need to reach a verdict in the case.

The defence has argued throughout the case that Thomas was mentally unwell at the time of the incident, saying there was a “gamut” of signs of psychosis.

The prosecution disagreed, saying he showed “clear thinking” ahead of the attack.

Greg Bull KC, for the prosecution, said on Wednesday that Thomas was not experiencing voices that told him to kill Mr Bush, as can happen in other cases of schizophrenia, and his searches for the veins and arteries of the neck suggested intent.

Orlando Pownall KC, for the defence, previously said the only explanation for the defendant’s actions was his mental state, and there was no “discernible motive” in the case.

Addressing the jury, he said: “You must acquit if you think there is a mental health explanation.”

The trial continues.