On December 23, 1985, police found the charred remains of a body from the smouldering rubble of a three-story manor house near Milford Haven, Wales.
Grisly clues at the crime scene would soon confirm to police that their worst suspicions were well founded.
Shotgun pellets were found in the wall of the first floor bedroom in which the body was found, while what appeared to be a blindfold or gag, having survived destruction by the flames, lay nearby.
Helen Thomas, 54, had been bound and shot, alongside her millionaire farmer brother Richard, whose body had already been found sporting a point blank entry wound to the stomach.
Those double murders at Scoveston Manor cast a shadow over what had been a sleepy part of rural West Wales, a pall which would darken considerably on June 29, 1989, when middle-aged Oxfordshire holidaymakers Peter and Gwenda Dixon were brutally executed on the pembroeshire coastal path.
What officers would later discover is that the weapon used on the Dixons was the same Belgian-made 12-bore shotgun that had belonged to Richard Thomas – the barrels of which Cooper had also turned on him and his sibling four years previously.
They were after the same man.
But who would have thought to consider oil rig worker-turned-farm hand John Cooper as someone worthy of scrutiny?
Barely a decade earlier, he’d won himself £90k and a new car worth four grand via a newspaper spot-the ball competition.
To anyone else, that would have been a life-changing amount – after all, the windfall was a vast sum back then (roughly the equivalent of £400,000 in today’s money).
And, for a while, life was good – Cooper used the cash to gift members of his family, take his wife Pat on luxury holidays to the US and even bought a small holding so the pair could grow crops and breed horses.
But a gambling addiction saw the wealth squandered, and soon any air of respectability he might have had in the local community – Cooper was a member of the Milford Haven Sea Angling Club and acting as an official at regional darts tournaments – became a mere mask to hide a far more sinister truth.
By night, the dad-of-two would stalk his neighbors’ homes, carrying out a prolific 1990s campaign of burglaries – using the hedgerow through which he’d creep, inching ever closer to his targets, to hide his cache of stolen goods afterwards.
Earrings, necklaces and silverware were all stashed around the Pembroke shire countryside , while curry powder was scattered in his wake in an attempt to deter any police dogs, brought in to help investigate the break-ins, from following his trail.
A masked Cooper even held up a terrified teacher at gunpoint at her home in nearby Sardis, but, when she wriggled free of the ropes he’d used to truss her up, she set off a panic alarm and he fled.
Nevertheless, he was arrested in 1998 after Dy fed-Powys Police’s Operation Huntsman inquiry into the multiple home invasions in the area finally caught up with him.
Police found hundreds of house keys hidden around Cooper’s then home in Jordanston, along with jewellery and other stolen items – so many, in fact, that the cache had to be laid out on trestle tables at Withybush Airfield so that they could be identified by their rightful owners.