As heir to one of Wales’ richest business dynasties, until last December Dylan Thomas had enjoyed a life of quiet privilege.

But on Christmas Eve morning the unassuming and ‘unconfrontational’ 24-year-old ended the life of his old school friend, William Bush, in an attack of almost unimaginable brutality.

Armed with two knives, Thomas targeted Mr Bush from behind, first stabbing him in the back of the neck. He then pursued the 23-year-old, inflicting dozens more wounds until he fell to the ground with blood pouring from his severed jugular vein.

The frenzied assault lasted seconds but the fallout will never go away.

For his victim’s family the loss of their loved one in such a savage way was as shocking as it was devastating.

Mr Bush had known Thomas since joining the same private school a decade previously. They holidayed, hung out and, finally, shared a house together.

But such is Thomas’ background that this was a crime that resonated beyond those directly involved.

His grandfather, Sir Stanley Thomas, left school at 15 to sell meat pies, establishing a business that grew into one of the most successful in Wales. It earned him and his family a £230 million fortune as well as money to invest in good deeds and rugby, their other passion.

Of course, money is no guarantee of happiness, something Thomas’s upbringing bore testimony to.

The court heard that his parents split when he was three and there had been ‘alleged domestic violence’. In fact, in 2003, his father, Scott Thomas, violently attacked his mother, a model who once graced the cover of Vogue.

Thomas Sr was jailed for six months at Cardiff Crown Court for the assault. This week, 21 years later, that same court was the backdrop for his son’s trial.

And one question was at the centre of the eight-day hearing: Why?

Thomas admitted killing his friend but denied murder, claiming diminished responsibility.

The prosecution case was that he knew exactly what he was doing and had planned the attack in advance, even studying the anatomy of the neck hours earlier.

It was suggested his ‘resentment’ of Mr Bush had been growing as the dynamic of their friendship changed, with Mr Bush planning on moving out to live with his girlfriend.

While Thomas did not give evidence in the case, watching via video link from Ashworth secure psychiatric hospital, it was claimed in his defence that he was psychotic at the time of the killing and had since been diagnosed with schizophrenia.

In the weeks leading up to the incident, the court heard, there had been signs of mental illness, with worrying comments made to Mr Bush and others. In a message addressed to Elon Musk, he offered to help him ‘solve gravity’.

Then, in November, Thomas was arrested having climbed over a fence surrounding Buckingham Palace. While in custody he was interviewed by a psychiatrist but released on bail – meaning he was free to kill his housemate.

Yesterday, following three hours of deliberations, the jury found Thomas guilty of murder. He will be sentenced next month.

His grandfather, Sir Stanley Thomas, was present in court throughout the trial - the man responsible for his family’s rags-to-riches tale.

Or, more accurately, pies-to-property-portfolios.

In the 1950s he and his brother, Peter, joined their father selling meat pies door-to-door.

‘I remember travelling all over the Valleys and Merthyr, starting at six in the morning and finishing at six at night,’ he once said.

Thomas Pies, as it was known, was sold in 1965 but five years later the brothers launched their own company, Peter’s Savoury Products, which grew into a business with a £70m turnover and 1,000 employees.

In 1988 it was sold for £75m, with the family investing in a property firm whose assets included airports in Cardiff, Belfast and Luton.

That firm’s subsequent sale boosted the family fortune by a further £100 million, making them regular fixtures in the Sunday Times Rich List.

In 2006, Stanley Thomas was knighted for his services to business, while his brother Peter went on to become chairman of Cardiff rugby club.

Sir Stanley’s son, meanwhile, found himself making headlines for very different reasons.

In 1998, Scott Thomas launched Cardiff nightclub Scott’s, inviting friends including Tara Palmer-Tomkinson and Simon and Yasmin Le Bon to the opening night.

The aim was to rival the ‘ambience, clientele and chic’ of London’s clubs.

But the venue shut after just one year after a clubber attempted to do handstand and died when he tumbled over a first-floor safety rail, falling 20ft onto the dance floor below.

By then Mr Thomas was dating Kirstie Howells, a statuesque blonde model ten years his junior who worked for Versace and Armani and had walked the catwalk with Naomi Campbell and Linda Evangelista.

In 2000, Dylan was born in Jersey, before the family moved to a mansion in the Old St Mellons area of Cardiff.

It was there in 2003 that the then 40-year-old Mr Thomas attacked his partner after returning in a ‘rage’ from a business lunch with his bank manager.

During his trial, the court heard how he had hurled her over his shoulder, slapping her and beating her head with a telephone and shouting: ‘I’ll kill you, I’ll kill you.’

Dylan was in the house at the time of the assault which left the walls spattered with blood and only ended when Miss Howells managed to flag down a passing motorist.

She later told friends: ‘I am rebuilding my life and facing up to the prospect of trying to explain to Dylan when he is older why his dad had to go to prison.’

An asthmatic child, Thomas was educated privately and it was at £44,000-a-year Christ College Brecon that he first met William Bush when he joined the school aged 13. The pair became ‘the closest of friends’.

Mr Bush, whose father is an English teacher, was a talented sportsman. He had a passion for rugby and would go on to play county golf. He was also popular, something of a contrast to his quieter and more introverted friend.

After school, Mr Bush went to university. Thomas meanwhile got a place at Cardiff Metropolitan University but left after a year.

He then moved into a £425,000 house in Llandaff, on the outskirts of Cardiff, that his grandfather had purchased as part of his property portfolio.

Mr Bush joined him there in 2021 and would help look after his friend’s labrador, Bruce.

Thomas was unable to drive – he had failed his theory test five times – and also relied on his housemate to ferry him around.

Alex Bush, the victim’s brother, told police: ‘Will had lots of friends. He was caring, perhaps too caring at times. Loyal, extremely loyal.

‘They would go on holidays together, not just holidays families paid for.

‘I know they went skiing together... I think Will kind of felt sorry for him and wanted to be there for him.

‘If Will came back home for Sunday lunch or to play golf he would make sure to get back because Dylan was on his own. He was just caring.’

Neighbours told the Mail that they were never troubled by loud music or parties. ‘We never had a peep out of them,’ said one.

Thomas, who was teetotal but did smoke cannabis, is listed as the sole director of three tech companies listed at the property and at the time of the killing had been working on virtual reality headset accessories.

Mr Bush had worked as a surveyor but had given up the job due to stress and ill health.

His girlfriend Ella Jeffries told police that he had shared concerns about his friend’s behaviour in the months before the killing.

That autumn he told her of an occasion when Thomas had said to him: ‘I thought or wondered about killing you’.

Mr Bush was concerned enough to barricade his bedroom door that night but Thomas did not attempt entry and they continued living together.

Then Thomas was arrested on November 6 having scaled a 14ft fence outside Buckingham Palace. The court heard he was rugby tackled to the ground by a police officer, who believed he was unwell and feared he could be shot.

He was bailed to appear in court in February of this year – having first been interviewed by a psychiatrist in what was described in court as a ‘missed opportunity’.

The incident had ‘concerned’ Mr Bush, his girlfriend said. Although he wanted to move out of the house, he did not want to leave his friend.

‘He wanted to look after Bruce, and Dylan was his friend and he wanted to make sure he was okay,’ she said.

The two men were due to have Christmas apart and Thomas spent the night of December 23 with his maternal grandmother, Sharon Burton, at her home in the Vale of Glamorgan.

Agitated and unable to sleep, in the early hours he did a Google search on the anatomy of the neck and found a medical illustration of the main blood vessels.

On Christmas Eve morning he asked his granny to give him a lift home so he could walk his dog.

Thomas also sent his friend a text message saying: ‘I need to see you before you go. Are you home?’ Mr Bush replied: ‘Yes, I’m home.’

Thomas arrived at the house at 11.16am and went inside where he apparently armed himself with a kitchen knife and a flick knife and went up to Mr Bush’s bedroom where he began the attack.

In a police interview Mrs Burton described how her grandson then emerged from the property, banging on the windscreen and saying: ‘He’s gone crazy.’

‘I jumped out and Dylan was just covered in blood and practically falling down on the floor,’ she said. ‘I ran into the house. I could see Will on the floor and straightaway I started to do CPR on him and didn’t stop until ambulance people came.

‘I thought I felt a pulse but I don’t know because my adrenaline was so crazy... His eyes were open. I thought I felt him moving but there was nothing there.’

During the interview Mrs Burton broke down in tears and said: ‘I wish I’d never taken him. I shouldn’t have taken him. I would never have envisaged anything like that from Dylan, not in a million years, because he’s such a quiet boy...’

When police arrived Thomas told them he had acted in self-defence saying Mr Bush had ‘gone mental’ and stabbed him with the knife after smoking cannabis. He told them: ‘He’s dead, I have f****** disarmed him.’

Asked where his friend had been stabbed Thomas said: ‘To the body there are stab wounds everywhere. To the body, on the face, on the neck, just f****** everywhere.’

Prosecution barrister Greg Bull KC claimed that Thomas ‘knew full well what he was doing’ and that it had been ‘a planned attack.’

He accepted that the motive was unclear, saying: ‘To all intents and purposes, they were good friends and that’s one of the mysteries of this case, we don’t know what caused Dylan Thomas to act in the way he did.

‘Whether it was a feeling of loneliness or resentment, despite having everything in life, Dylan Thomas had achieved very little.’

Mr Bush, by contrast, was about to start a new job, had a girlfriend and was looking to move out.

‘Everything in his life was on the up where it might have been perceived in Dylan Thomas’ case, life was on the downward spiral,’ said Mr Bull.

But evidence presented by the defence suggested he had been experiencing psychosis for up to six months before the event.

Dr Panchu Xavier, a forensic psychiatrist treating Thomas at Ashworth, said his family noticed changes in his behaviour but did not realise they were signs of psychosis.

These included discussions about teleportation, witches and the Illuminati.

Of his arrest in November, Thomas had told the medic he had climbed the fence ‘because he was trying to explore energy fields between Buckingham Palace and Cleopatra’s Needle’.

Following his arrest, he had asked police: ‘I’m over now, do you mind showing me round the palace anyway?’

Drawings and letters by Thomas addressed to Elon Musk were passed to the doctor.

One message sent to the Tesla founder was entitled ‘Gravity’ and read: ‘Dear Mr Musk, once you solve gravity you can solve everything else. Have learnt everything about everything in a short period of five months.’  

Thomas also claimed Mr Bush had once said to him: ‘I’d like to drink your spinal fluid’. The psychiatrist said this was clearly an auditory hallucination.

On the attack itself, Dr Xavier said: ‘It’s not uncommon for people with psychosis arming themselves with weapons if they believe they are going to be harmed. (Thomas) believed in some way he was going to be harmed, that’s his account.’

Of course, the reality was very different and, to the last, Mr Bush had remained his one true friend.

When police asked his girlfriend to describe him, she replied: ‘Kind, caring, funny, loving – he’d go out of his way for anyone to try and help someone.’

Loyalty and compassion that ultimately could be said to have cost him his life.