DASH-CAM footage from PC Andrew Harper's undercover BMW police car was shown to the jury at the Old Bailey.

*Warning: bad language* 

PC Harper died on August 15 after being dragged behind a car for more than a mile at speeds of around 40mph.

He and his crewmate PC Shaw, who can be seen on the video, had responded to a call for burglary three hours after their shift had ended.

READ the latest from the Old Bailey murder trial. 

In the footage, they can be seen driving down a narrow country road before they meet the Seat Toledo - the car at the center of the murder investigation - head-on. 

Henry Long, the driver of the car, and two 17-year-old boys, who cannot be named for legal reasons, deny his murder.

The video then shows somebody wearing a face-covering trying to get into the back seat of the car as the quad bike that was towed behind rolls away. 

The Seat then moves around the police car and a loop can be seen trailing behind. 

The video goes on to show PC Shaw reverse down the road before he says 'Ah F***!'

PC Shaw then says 'wait 1' to a call handler who is asking for his location. He previously told the court that this meant he needed to gather his thoughts. 

PC Shaw then tells the operator that he has lost his crewmate, saying 'my colleague PC Harper got out of the vehicle to run after the vehicle, I've now lost him'.  

He says the car will come out on the A4, 'just down from Sully' - the police training centre. 

PC Shaw then stops the car as he finds PC Harper's stab vest in the road.