Barry Rogers this afternoon (Monday) denied changing his story to back up his claim that his grandmother Betty Guy died before he got to her.

And he claimed his mother was in the habit of serving Mrs Guy tea laced with cannabis.

Rogers had told a jury at Swansea crown court he arrived at Mrs Guy's home in Hillcroft, Johnston, after his mother Penny John had already dialled 999 to report her death.

Rogers was accused today of going back on what he told police after his arrest to make it look as though he had not had the opportunity of killing her.

Rogers, of High Street, Fishguard, and John, 50, of Union Terrace, St Dogmaels, deny murdering Mrs Guy in the early hours of November 7, 2011.

At first her death was put down to natural causes and her body was cremated at Narberth four days later.

Rogers was cross examined today by Paul Lewis QC, the barrister leading the prosecution.

The jury has heard how Rogers had been at home in Frome, Somerset, late on November 6, 2011, when he received a telephone call from his mother telling him his Nan was seriously ill and that she was asking for him.

Mr Lewis reminded Rogers that he told police he had left about 11pm, had driven at 140mph and that the journey had taken about two hours.

But on Friday he had told the jury he had left about midnight, driven at between 90mph and 100mph, and that he had arrived between two and a half and three hours after leaving.

Mr Lewis accused Rogers of altering the details to support his claim that he arrived too late to say goodbye to her - or to smother her with a pillow, as alleged.

Rogers revealed that his mother served his grandmother tea laced with cannabis, which she later referred to as "mum's special tea."

"My mum told me she used to put cannabis in her tea. It was towards the end of her life.

"It was at my Nan's request, my mum said.

"I have never told the police before because it was never a question that was put to me."

Mr Lewis said police officers had asked him: "Any drugs given to your Nan? And you said 'no.'"

Rogers: "I did not want to get my mum into trouble."

After their initial arrest police granted Rogers and John bail as long as they stayed together at John's home, which officers had secretly bugged.

During tape recorded conversations John could be heard saying to Rogers that they must not mention anything about giving Mrs Guy illegal drugs.

"You decided that together," said Mr Lewis. "Don't tell the police about mum's special tea."

Rogers said he understood his mother obtained the cannabis and gave it to his grandmother, who may have mixed it into her tea herself.

"I was not aware of it (the cannabis) until after she died," he added.

The trial continues.