THE road where police officer Andrew Harper was dragged to his death last August was "a very narrow country lane" where visibility was limited, an expert has said.

The Old Bailey heard Lambdens Hill near the village of Sulhamstead in Berkshire has a limit of 60mph but drivers would have been advised not to reach that speed.

PC Harper, 28, died from multiple injuries when he was pulled along behind a car after responding to the reported theft of a quad bike late at night on August 15.

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Henry Long, 18, from Mortimer, Reading, and two 17-year-olds, who cannot be named because of their age, all deny murdering the Thames Valley Police officer.

They all admit conspiring to steal a quad bike, and Long has admitted manslaughter, which the younger defendants deny.

Giving evidence in the trial on Friday, collision reconstruction expert Simon Hall described Lambdens Hill as a "minor country road", around 3.4 metres wide (11.2ft), and with a road surface of granite chippings.

He said: "It is a very narrow country lane."

Asked by prosecutor Brian Altman QC about whether it was possible to drive at the 60mph speed limit, Mr Hall said: "You could drive it, but I wouldn't advise it.

"Certainly on the bendy sections, it would be very difficult.

"On the corners you couldn't see if anything was coming the other way."

The court previously heard that PC Harper and crew mate PC Andrew Shaw were driving along Lambdens Hill on their way to the call when they met a Seat Toledo, driven by Long, coming the other way.

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One of the 17-year-olds was in the passenger seat, and the other was riding the quad bike which was being towed behind the car, attached to the boot lid hinge with a crane strap that formed a loop.

As the cars met, the teenager on the quad bike dismounted, disconnected the strap from the bike and tried unsuccessfully to get into the passenger door of the Seat, as Long began to drive off, the jurors heard.

Prosecutors said PC Shaw turned the police BMW's emergency lights on, and the teenager ran to jump through the back passenger window of the Seat.

As PC Harper tried to stop him, the officer's feet were encircled in the crane strap, and he was dragged along as Long drove off, jurors were told.

The court heard that Long drove at an average speed of 42.5mph, leaving a snaking trail of tyre marks, blood and clothing as he swerved across the country lane.

The trial continues.