A video from Snapchat shows driver Ricky Davies drinking alcohol at the wheel of his Ford hours before the crash that would kill 18-year-old Dafydd Hughes.

Episode two of series four investigates the circumstances surrounding the death of Dafydd Hughes, from Abertysswg after he was a rear seat passenger in Davies’ car while he was drunk and high.

The second episode aired on BBC One tonight, October 16, with the opening words describing how the passenger in a “looks in a really bad way”.

Crash investigator Bob Witherall then arrives on scene on the B4235 between Chepstow and Monmouth where a Ford Focus has crashed head-on with a Peugeot.

He discovers serrated marks which illustrated “the wheels were rotating while the vehicle slid sideways” as the Peugeot swerved to avoid the Focus which was “completely on the wrong side of the road”.

Witherall assumes the car was speeding and is proven right, with the car revealed to have been driving at well over the 40mph speed limit. The damage to both cars was so severe that gouge marks where inner vehicle parts had hit the floor were clearly visible.

Strongbow cans are found in the car following a “strong smell of booze”. A colleague remarks the crash has caused “a waste of a life” after Hughes sustained a significant head injury.

No one in the vehicle was wearing their seatbelts, and Witherall notes if he had been, Hughes “would probably have survived”.

South Wales Argus: Dafydd Hughes was a rear-seat passenger in the car at the time of the crashDafydd Hughes was a rear-seat passenger in the car at the time of the crash (Image: Gwent Police)

The episode captures the moment police are informed of a video making the rounds on social media. Upon viewing the clip, Witherall is horrified to see how intoxicated Davies is while driving.

He says: “One of the passengers even says 'look at the mess of my butty'. They realised what a mess he was in, how intoxicated he was, but they still think it was acceptable to be in the car egging him on.

“He is using the steering wheel with two fingers while he drinks can of cider out of his left hand. There is minimal control of vehicle. It was a recipe for disaster. Looking at how intoxicated he was I am amazed they got as far as they did.”

South Wales Argus: The episode covers Davies’ police interview and recounts his story depleting after being confronted with the Snapchat footage.

Police discovered Davies had been on a three-day drink and drugs bender with no insurance or licence when he took his friends to a dog show in Usk.

Witherall concluded that what he’d seen was “a complete and utter criminality and disregard”. He said: “Ultimately, his actions led to the death of his best friend and he’s got to live with that and deal with it.”

In a tribute to Dafydd, his family said: "Dafydd made the most of his life and was always smiling. He loved fishing and going to dog shows. He was a proper boy. Dafydd was a loving son, grandson, brother, nephew and dear friend and will be greatly missed."

Davies, of Aneurin Terrace, Rhymney, was found with over the drink drive limit of alcohol in his blood hours after the crash. He was sentenced to eight years in prison.

Crash Detectives continues on BBC One, 7pm, Mondays.