A MAN died of "major and serious burns" to 60 or 70 per cent of his body after his caravan was engulfed in flames, a jury has heard.

Richard Thomas died at a specialist burns unit in Bristol hours after members of the emergency services pulled him from his burning home near Magor on December 20 last year.

Today at Cardiff Crown Court, 43-year-old Darren Smith was put on trial accused of Mr Thomas' murder.

Opening the trial, prosecution barrister Michael Jones KC accused Smith of murder by "a combination of blows and setting a petrol-fuelled fire" against the alleged victim.

He told the jury "this defendant assaulted Mr Thomas in his own caravan, leaving him lying on the floor injured and incapacitated".

"The defendant then set fire to the caravan using an accelerant," Mr Jones said, adding that Mr Thomas was "unable to get out of the burning caravan".

Mr Thomas and the defendant lived in neighbouring caravans and had a "somewhat volatile relationship", the court heard.

Mr Jones said the pair had been involved in an "altercation" three days earlier, after which Smith had sent messages to his mother, alleging Mr Thomas had threatened him.

"I don't need that, but if he does it again I would have to hurt him," Smith wrote to his mother, Mr Jones said.

Jason Pritchard, whose father owns the caravan park, told police he had been woken by dogs barking in the early hours of December 20, and when he looked out of the window he noticed what he thought was steam above Mr Thomas' caravan, and "saw this defendant in his dressing gown walking calmly away... to his own caravan", Mr Jones said.

When he realised the steam was in fact smoke, Mr Pritchard went into the alleged victim's caravan and found him "severely injured" on the floor. He attempted to extinguish the fire and remove Mr Thomas from the caravan, before calling 999.

When the emergency services arrived they treated Mr Thomas for his "horrific and devastating" injuries, anaesthetised him and sent him to the Southmead Hospital in Bristol.

"The defendant came out of his caravan and went over to try engaging the police and fire officers in conversation," Mr Jones said. "He said he knew nothing about the fire and suggested Mr Thomas might have taken his own life."

One officer "noticed soot on [the defendant's] nostrils" and asked Smith if he had been in the burning caravan, but Smith said "it was because of his own log burner".

Smith was arrested later that morning and then - following Mr Thomas' death that day - charged with the 52-year-old's murder, which he denies.

Mr Jones said Smith initially told police at interview "at no point did I start any fire" but during a fifth round of questioning gave another prepared statement "said he did see Richard Thomas... did go inside the caravan... and was with him when the fire started".

Smith told police Mr Thomas picked up a jerry can of petrol and poured its contents on the floor, Mr Jones added, saying the defendant was "claiming Mr Thomas set fire to himself in his own caravan".

The defendant then told police he had washed his dressing gown, burned his trainers "so the murder wasn't pinned on him".

Smith, then of The Beeches Residential Caravan Park, denies murdering Mr Thomas. The defendant will be represented by David Elias KC.

The trial before judge Tracey Lloyd-Clarke continues.