A man who killed his housemate in Cardiff on Christmas Eve had previously told him he’d thought about murdering him, a court has heard.

Dylan Thomas, 24, has pleaded guilty to the manslaughter of William Bush, 24, in December 2023, but denies murder.

Cardiff Crown Court heard that the pair had met at school at Christ College in Brecon and had been friends since.

Mr Bush was popular but “Dylan Thomas had few friends and was viewed as something of a loner,” said Gregory Bull KC, prosecuting, adding his “only real friend was the deceased”.

The court heard that the pair lived together at a house in Chapel Street, Llandaff.

The “dynamics” of their close friendship began to change when Mr Bush got a girlfriend and was planning to move in with her.

In late October, Mr Bush had told his girlfriend Ella Jeffries that he had barricaded himself into his bedroom one evening after a discussion with Mr Thomas.

The court was told that Mr Thomas had told Mr Bush: “I thought and wondered about killing you. I just wanted to see what would happen if I do certain things.”

Mr Bush told his girlfriend it had left him feeling scared.

On 23 December, Mr Thomas went to stay with his grandmother in Rhoose, Vale of Glamorgan.

Mr Bush had planned to spend that evening with his girlfriend and then Christmas with his family in Brecon.

At his grandmother’s house, Mr Thomas seemed unsettled, the court was told.

Mr Bull said at 00:36 on Christmas Eve, Mr Thomas carried out a search on his computer for the “anatomy of the neck” and then at 02:42 he sent Mr Bush a text message saying he needed to see him before he went to Brecon for Christmas.

Mr Bull said that indicated that Mr Thomas was formulating an intention to kill William Bush.

At 03:31, Mr Thomas tried to book an Uber taxi to take him to Chapel Street, but was unable to.

The following morning his grandmother, Sharon Burton, agreed to drive Mr Thomas to Llandaff, because he said he wanted to walk the dog.

On the journey, Mrs Burton described him becoming “more and more agitated” and was sending several text messages.

She parked outside the property while Mr Thomas went in.

The prosecution say he then armed himself with two knives, one large kitchen knife, and another flick knife, and went up two flights of stairs to Mr Bush’s bedroom, where an attack began.

Mr Bush sustained a total of 37 stab wounds, which included 13 to the front and side of his neck, eight to the back of his neck, seven to the front of his trunk and eight to the back of his trunk.

He also suffered a slash to his face, a cut to his ear and 13 cuts to his left hand.

Mrs Burton, who has hearing loss, then saw Mr Thomas banging on her car window distressed.

“Passers-by heard screams of horror coming from the address,” said Mr Bull.

Mrs Burton then found a wounded Mr Bush on the patio outside the property and she began to give him CPR.

The jury’s been shown police body worn camera footage in which Mr Thomas, wearing a heavily blood stained top, told police he had been hurt and was acting in self-defence.

The footage also showed, Mr Thomas telling police that Mr Bush was dead and that he disarmed him.

“This was a planned attack,” said Mr Bull, “He deliberately armed himself with knives and attacked him from behind.”

Mr Bull told the jury that Mr Thomas is being treated for schizophrenia at Ashworth High Secure Hospital on Merseyside, from where he’s appearing via videolink.

Mr Thomas denies murder and the trial continues.