ITV's The Pembrokeshire Murders, is based on a rather unusual true story. The drama, which wrapped on Wednesday with 6.6m viewers tuning in for the finale, explored the double murders of siblings Richard and Helen Thomas in 1985 and the double murders of Peter and Gwenda Dixon, which remained unsolved for more than 20 years.
In 2006, then-newly promoted Detective Superintendent Steve Wilkins, played by Luke Evans, decided to reopen both cases, employing pioneering forensic methods. Wilkins and his team found microscopic DNA and fibres that potentially linked the murders to a string of burglaries.
"I was aware that there was one slide which had been retained from the Thomas's murder scene which had never been examined and the reason being is that they were told that by opening, they could actually destroy what was in it," the real Steve Wilkins tells Tyla.
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The crimes were committed by John Cooper, the Welsh serial killer and diagnosed psychopath, played by Keith Allen. He was sentenced in 2011 for both double murders.
Cooper was sentenced to 16 years behind bars in 1998 at Swansea Crown Court for 30 counts of burglary and a robbery. He was released in January 2009.
"He's quite spooky to look at and for me he actually captured the essence of Cooper perfectly.
"I was aware that Cooper was going to be possibly paroled and if he killed four people, he was likely to kill again. I was also aware that it was unlikely for the next five years that forensic technology was going to progress much further," explains Steve as he describes why the case was reopened in 2006.
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Steve and his team made the decision to open the slide and though it did not contain evidence needed for the investigation, it did set off a chain of events.
Since the murders in the 1980s, there had been an advancement in forensic science and in investigative techniques as well, both of which encouraged Steve to re-open the case. "A combination of historical offences, and the material and exhibits have been retained from those offences and as long as you could prove the integrity of those exhibits, it was just the right time now to start applying modern day techniques to those offences."
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Cooper appeared on the TV game show Bullseye in May 1989, in the month before the murders of Peter and Gwenda Dixon. Steve Wilkins was at a pub after his son's football match and discovered it was the pub where Cooper used to drink.
There was a picture of Cooper on the board because he happened to be the captain of the darts team. The landlord tipped Steve off that Cooper had been on Bullseye years before. With the help of Welsh ITV journalist Jonathan Hill, who had been covering the case, Steve Wilkins, managed to track down the footage at the ITV archive in Leeds.
"When Steve and I were discussing the case, he knew so much about Cooper's background and one of the things that was thrown in there was, 'Oh, he's been on Bullseye' and when you mention that everyone is curious, and their ears prick up, but we didn't know the significance of that appearance," Jonathan explains to Tyla.
"When we followed the paperwork, and amazingly it still existed, we discovered that they recorded those shows in May 1989, which suddenly made it a month before the murders."
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An archivist trawled through Bullseye episodes to find the one featuring Cooper. Only the first name of the contestant is shown which made the search more difficult, especially due to Cooper destroying all pictures of himself from that period. However, they did have a photofit of a man seen using Peter Dixon's cash cards following the murders and when the pair compared the photofit to Cooper on Bullseye, it was a perfect match.
"This was the first time we actually had a photograph, which I could confidently say, this is how John Cooper looked at the time that the Dixons were murdered," says Steve. Cooper had destroyed all pictures of himself at the time of the crimes, executive producer Simon Heath previously explained.
The artist's impression features a man with khaki shorts and of the key forensic developments was a minuscule speck of blood found in a pair of women's khaki shorts that Cooper had taken from one of his victims. Cooper asked his wife, Pat, who was an accomplished seamstress, to alter the shorts.
"We asked them to do some fibre lifts and by doing that, they noticed a dark stain that was tested and that came out as Peter Dixon's blood. So that was the first forensic hit.
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"When we asked them to unpick the hem, sealed in the hem was other blood, and also there was fibres linking him to a rape and attack on the five children and in the pockets of the shorts, there were fibres, which were identical to fibres taken off Richard Thomas, from the first double murder.
"So we had actually connected four murders, a rape and indecent assault and five robberies. An amazing yield of forensic evidence from one garment."
Steve and Jonathan spent time on set during filming to help the cast understand the ins and outs of the case. Steve even spent time with Luke's family in Cardiff. "I think what came across to me was, was his compassion, and his understanding.
"It was quite clear that he was well read in relation to the actual, the investigation itself and we spent some time just over a beer just talking." After visiting the cast on set, Luke took notes and made alterations to his script to perfect his performance as Steve.
After being released from prison in January 2009 Cooper was arrested in May 2009. He was convicted in May 2011 for both double murders and he was also sentenced for the rape of a 16 year-old girl and a sexual assault on a 15 year-old girl committed in 1996. Both of the latter crimes were carried out at gunpoint in Milford Haven, Pembrokeshire.
Cooper's appeal against the conviction was rejected in November 2012. He remains behind bars.
Featured Image Credit: ITVTopics: TV and Film, Luke Evans, ITV