The 76-year-old monster is serving life for four murders in Pembrokeshire, west Wales.
Cooper shot brother or sisters Helen and Richard Thomas at their manor house near Milford Haven in 1985.
Serial killer John Cooper hid 500 sets of house type in the cesspit at his house as mementoes, the Mirror can expose.
4 years later on, he killed couple Peter and Gwenda Dixon on a coastal path near Pembroke.
It was seen by millions previously this week.
” He begins to get confronted by homeowners so progresses to break-in and that control and the disproportionate violence would sexually excite him.
Video from his appearance on Bullseye in 1990 assisted cold-case evaluation officers nail him 21 years on, by matching his search the gameshow to a sketch of the suspect.
” He believed of himself as a business person after winning ₤ 98,000 in a spot-the-ball competition– about ₤ 300,000 in todays cash.
” He then buys a race horse for ₤ 2,000 however brings it back on the motorway in a cheap horsebox with a rotten floor, so the poor horse falls through the flooring on the freeway and breaks its legs.
He added Cooper had a substantial ego and kept trophies from victims to “re-live that control” he had over them.
” He frittered away his payouts but when asked about it, it was always somebody elses fault.”.
His victims consisted of brother and sister Richard and Helen Thomas.
( Image: ITV).
” He resided in a backwoods surrounded by fields and used to prowl those fields in the evening.
” He started out as a Peeping Tom– he would always assault females in houses backing on to fields. After that, he advances to burglary realising he can steal items and cash he can utilize to money his addictive gambling.
The retired Dyfed-Powys officer, now 61, stated: “Here is a guy that began as a prolific dwelling home intruder and his MO was constantly the exact same.
A selection of 503 secrets cops recuperated from a cesspit at John Coopers home
( Image: Athena).
” He all of a sudden chooses, Were going to be turkey farmers, and it stops working immediately.
And previous Det Supt Steve Wilkins, who brought Cooper to justice, informed The Mirror how he went from Peeping Tom and burglar to savage killer.
” Then we get to the sexual component of his crimes.” When Mr Wilkins started his examinations in 2006, Cooper was currently serving 14 years in jail for a string of violent raids.
John Cooper was responsible for The Pembrokeshire Murders.
( Image: REX/Shutterstock).
” He was a coordinator. He understood the hedgerows, the nighttime landmarks … he used to cut fences in a manner in which helped him if he had to escape.
Providing an insight into the killers mind, Mr Wilkins said Cooper had “a very inflated viewpoint of himself”.
Much of what Cooper had taken was “useless”, Mr Wilkins said, however that did not stop him keeping “trophies” at his Haverfordwest house.
The probe into the Cooper was become a book and a three-part ITV drama starring Luke Evans and Keith Allen.
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” When they browsed his house, they discovered 500 sets of keys hidden in the cesspit,” Mr Wilkins said. “The shorts which had DNA which caused his conviction, he took from Gwenda Dixon when he murdered her.”.
John Cooper murdered Peter and Gwenda Dixon.
( Image: ITV).