The jury also cleared Morgan, 28, of two charges of damaging property with intent to endanger life, when he drove a bulldozer during a protest against animal carcass burials in mid Wales.

Stephen Morgan denies the charge

The jury also found the farm worker not guilty on three separate counts of damaging property and being reckless as to whether life was endangered.

The jury will return to their deliberations on Wednesday after failing to reach verdicts on two outstanding matters.

One charge, of damaging property with intent to endanger life, relates to Pc Stone.

The second charge, damaging property while being reckless as to whether life was endangered, relates to a tent at an army checkpoint.

The prosecution had claimed that Morgan, 28, deliberately rammed police vehicles in a stolen bulldozer in a drunken bid to prevent carcasses being buried on an army range at Sennybridge near Brecon.

Mr Morgan, of Bronallt, near Llandovery, had denied the charge of attempted murder.

He claimed he had lost control of the 50-ton vehicle before it crushed a police van, while Pc John Stone was still at the wheel.

Swansea Crown Court has heard how Mr Morgan was at the controls of the earth-moving machine when it went on a two-mile rampage in the early hours of 1 April.

It finished with the police officer being left trapped in a squad car squashed to below waist height.

Pc John Stone: Terrified

Mr Morgan told the jury he knew he was committing a criminal offence when he climbed into the cab of the bulldozer and set off to block the road leading to the proposed burial site on Eppynt mountain near Brecon.

He was one of up to 150 protesters trying to blockade the army range at Sennybridge, Powys, which had been earmarked as a disposal site.

He said he believed it was better to have broken the law than to have allowed diseased carcasses to ruin the Welsh countryside and had refused offers of work on the burial ground for that reason.

Mr Morgan denies attempted murder and damaging seven vehicles with intent to endanger the lives of their occupants.

'Mown down'

Earlier in the trial, he was cleared on the directions of Mr Justice Roderick Evans of damaging two Ministry of Defence vehicles and assaulting a soldier.

Under cross-examination in the trial, he said that he did not see the police van containing Pc Stone until he had run over it.

He also said he had no idea he had mown down an army checkpoint.

Mr Morgan, who is licensed to drive heavy machinery, said he had drunk eight pints of lager before climbing into the cab of the machine and setting off from a contractors' compound on the mountain.

The defendant admits dangerous driving

As the bulldozer began to descend a hill, he hit a police Transit van and began pushing it down the road.

He said he was concentrating on this, and looking to his right, when he collided with the van containing the police officer.

He admitted squashing the van but said he had not realised at the time that he was running over a vehicle and that someone might have been inside.

He admits aggravated vehicle-taking and dangerous driving.

After the incident, he made his way to an empty farmhouse where occupiers returned hours later to find him in bed, naked and asleep.

Country road

Pc Stone told how he was trapped in his wrecked van for two hours after colleagues looked on in the belief that he had been crushed to death.

He said he initially thought that his colleagues were escorting the bulldozer down the country road leading to the army range.

But protesters and police fled in panic as the vehicle's lights dazzled him, leaving him no time to escape.

He was released from hospital after five days suffering a broken ankle, cuts and bruising to his head, shoulder and chest, bruising to his eyes and cuts to his hands.

He was unable to return to full-time duty for five months.