Scoveston Park farmer Richard Thomas was shot in the head as he tried to escape his "merciless" executioner, a jury heard today.

Mr Thomas, a millionaire, arrived home late on December 22, 1985, as farm labourer John William cooper was in the process of robbing is sister Helen, it was alleged.

Gerard Elias QC, prosecuting, told Swansea crown court that Mr Thomas' body was found on the landing inside the burned down house.

But forensic examination of the scene showed that it appeared he had been hit in the head by a "raking" shot from a 12 bore shotgun, probably as he tried to run away.

He took refuge in an outhouse, but Cooper allegedly cornered him and killed him with a shot to the abdomen which was fired when the muzzle of the gun was actually touching his body.

Then a blanket was used to wrap the body and drag it into the house, added Mr Elias.

Detectives found a pool of blood in the outhouse as well as lead cartridge pellets and wadding.

And the driver's side door of Mr Thomas' car was still open when police arrived.

Mr Elias said Miss Thomas, aged 56, may have been tied up and left on a bed upstairs in the house, and she had been gagged or blindfolded with a man's shirt. After the fire had taken hold her body fell through to the ground floor below.

"The prosecution say the need to kill the Thomases no doubt arose because the intruder was afraid that whether by voice or action or appearance he might be recognised or known.

"The defendant had worked for Richard Thomas," added Mr Elias.

He described their killer as cold and calculating.

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.