The true crime drama The Pembrokeshire Murders came to a conclusion on Wednesday night with 7 million people watching the final episode of the series, with the drama drawing in ITV's biggest overnight audience average since 2014.
The series had an average of 6.6 million people tuning in to see the finale as the drama followed the investigation into two double murders that shook Pembrokeshire in the 1980s.
The drama, starring Luke Evans, launched on Monday with 6.3million viewers glued to their screens.
ITV Wales Presenter Jonathan Hill who covered the original case said: "I couldn't believe it when I ended up playing a small part in the case.
"Detectives believed Cooper had taken part in the ITV game show 'Bullseye' and they asked me to help find the footage in the archives.
"We eventually tracked down the footage and incredibly it turned out to have been filmed just a month before Cooper killed the Dixons.
"The image of him playing darts for the star prize on the show also bore an uncanny resemblance to that artist's impression of the killer all those years ago.
"That image went on to become part of the key evidence that saw Cooper convicted and jailed for life for the murders."
A documentary looking at the true story behind the murders - The Pembrokeshire Murders: Catching the Game Show Killer - will be shown on ITV on Thursday 15 January at 9pm.
The documentary The Pembrokeshire Murders: Catching the Game Show Killer will be shown on ITV on Thursday 15 January at 9pm.