The body of murdered farmer Richard Thomas had been covered with "stacks" of newspapers and debris around the body of his sister contained diesel, a jury has heard.

Swansea crown court has been hearing what firemen discovered as they tackled a major blaze at Scoveston Manor late on December 22, 1985.

The prosecution say Richard and Helen Thomas were shot dead by John William Cooper, who then set the fire.

Then fire officer Richard Brock said he saw the body of Richard Thomas lying on stairs. To enable the body to be retrieved he had to remove "stacks" of paper, some of which were still burning.

The building was unsafe and debris was falling onto the firemen, he added. Shortly afterwards the roof collapsed.

The Divisional Fire Officer Michael Henry George said he spotted the fire from his home nearby and he drove to the scene.

He was told that a body had been seen and he entered the burning building. But there was a danger of the house collapsing "and a shout went up to evacuate the building."

The body of Helen Thomas, aged 56, was not found until 10am the following day. She appeared to have been lying on a bed upstairs and the bed had fallen through the floor during the fire.

Alexander Ian Grant, then a forensic scientist specialising in fire scene analysis, said he went to Scoveston Manor at the request of the police.

Helen Thomas' body was still inside a downstairs room and had been extensively burned.

The blaze had been so severe, he added, that it proved impossible to say where it had started or how many seats of fire there had been.

But there had been one major seat of fire in the bedroom where Helen Thomas had been.

Diesel residue was detected on debris around her body, the bottom step of the stairs and on a blanket and clothing recovered from a half landing.

In his view, he said, the fire had been started deliberately using diesel.

Christopher Wayne Davies, of Haverfordwest, said he lived in Rosemarket during the 1970s and he got to know Cooper when Cooper and his family moved into the Big House in the village.

Mr Davies said he had worked for Richard Thomas as a casual labourer and he had seen Cooper working "on the hay" at both Scoveston Manor and Norton Farm, which Mr Thomas also owned.

He had also seen Cooper talking to Mr Thomas on one occasion about buying bags of corn from him.

Gerard Elias QC, prosecuting, has alleged that the Thomases were killed during a robbery because the couple may have recognised their attacker.

Cooper, aged 66, of Spring Gardens, Letterston, denies the murders, and the murders of Oxfordshire couple Peter and Gwenda Dixon, aged 51 and 52. They were tied up and shot while enjoying a last walk after a two week holiday in Pembrokeshire in June, 1989.

Nine years later Cooper was jailed for 16 years for 30 burglaries and a violent robbery.

Items found by police during Operation Huntsman, which led to his arrest, were subjected to new forensic analysis between 2007 and 2009 as a result of which Cooper was charged with four murders, rape, indecent assault and five attempted robberies.

Cooper denies raping a 16 year old girl in a field close to the Mount Estate, Milford Haven, on March 6, 1996. He also denies sexually assaulting her friend and trying to rob five teenagers of cash.

The trial continues.