A brave young police officer was killed "in the line of duty" in "truly shocking circumstances" as he attempted to stop three teenagers from stealing a quad bike, a trial has heard.

Jonathan Laidlaw QC, the prosecutor in the trial of three teenagers for the murder of Pc Andrew Harper, has begun opening the case.

Pc Andrew Harper was dragged for more than a mile of winding country road, his uniform gradually stripped from his body, after his ankles got caught in a tow rope attached to the thieves' car.

Henry Long, 19, drove at speed along the lane in Berkshire on the evening of August 15 last year, in such a fashion that the stricken officer was "swung side to side like a pendulum in an effort to dislodge him", the Old Bailey heard.

Pc Harper eventually became disentangled but died from his injuries in the road.

Prosecutor Jonathan Laidlaw QC said: "Pc Harper was killed in truly shocking circumstances.

"During the course of that high-speed journey, and until at last he became disentangled, his police uniform was quite literally ripped and stripped from his body.

"Pc Harper was left as you can imagine with the most appalling of injuries, from which he died there on the road.

"It was a senseless killing of a young police officer in the line of duty, a young man who was doing no more than his job."

Long has admitted the manslaughter of 28-year-old Pc Harper, but has denied intending to kill him.

He is on trial for murder, along with Jessie Cole and Albert Bowers, both 18, who were his passengers.

Jurors were told they had been trying to escape police, having been caught in the act of stealing a quad bike.

The court heard homeowner Peter Wallis had reported masked thieves making off with the valuable Honda quad bike from his house in Bradfield Southend, near Reading, at 11.17pm.

Pc Harper, known as Harps, and his colleague Pc Andrew Shaw, were in the area in an unmarked police BMW when they responded to the 999 call, more than four hours after their shift was due to end.

Mr Laidlaw said: "Despite it being well beyond the end of their shift, because they were close and thought they could help, they responded to the call.

"Going beyond the call of duty, as it were, would cost Andrew Harper his life."

Cole, from Aldermaston, and Bowers and Long, both from Mortimer, Reading, have admitted conspiring to steal the quad bike but deny murder.

Jurors have been told the case is being re-tried after the original trial, which began in February, was abandoned due to the coronavirus pandemic.

On Monday, judge Mr Justice Edis described the victim as a "brave young" officer, but told jurors they must decide the case in a "fair-minded and clear-sighted" way, despite any thoughts of "admiration" for Pc Harper's actions on the night he died.

The trial continues and is due to last up to five weeks.