A man was being held on suspicion of attempted murder last night after a stolen bulldozer crushed a van carrying two policemen during a night-time rampage at a disputed foot-and-mouth burial site.
The 30-tonne excavator was taken by an unidentified driver from a compound at an Army firing range in mid-Wales which has been the focus of protests against a planned disposal pit for animal carcasses.
Forensic experts were yesterday examining a two-mile "trail of destruction" after the digger ploughed through a checkpoint and into a series of parked vehicles, scattering police and protesters.
A 38-year-old officer was recovering in hospital from leg injuries after the bulldozer rode over the rear of his van, trapping him for more than two hours in the wreckage of the driver's cab.
His colleague, sitting in the passenger seat, managed to flee before the caterpillar-tracked digger crushed the van and struck other police and Army vehicles before careering off across fields.
Officers chased the heavy-duty excavator before it was brought to a halt on the adjoining A40 road to Sennybridge, near Brecon. A man was arrested nearby and taken into custody with three others.
A Dyfed and Powys Police spokesman said: "The alleged driver is being questioned on suspicion of attempted murder. This was an extremely serious incident."
The incident at Eppynt Mountain happened at about 1.45am as more than 50 demonstrators were staging a blockade of the site to halt its use for burning and incinerating thousand of slaughtered livestock.
Witnesses described how the vehicle suddenly loomed out of the darkness, criss-crossing a narrow country lane as it descended a hill at around 25mph.
Glyn Powell, the deputy leader of the Farmers' Union of Wales who was taking part in the protest, said: "The bulldozer just came out of the darkness, heading for parked cars and other vehicles.
"We were all scattered, we could have been slaughtered. It just carried on going, ploughing on through hedges and fields. This driver was skilled in what he was doing."
Fire-fighters cut the trapped police officer, who had been seconded from South Wales Police to help colleagues in the Dyfed and Powys force, from the crushed remains of the van.
He was yesterday recovering in hospital at Abergavenny after doctors found he had escaped with severe bruising instead of the major leg injuries he was initially believed to have suffered.
Terrence Grange, chief constable of Dyfed and Powys Police, said it was fortunate that protesters and other police personnel had escaped injury.
He said: "This is an absolute horror. It must have been a terrifying thing to go through. It was not just officers, everybody was fleeing for their lives.
"The officer is badly bruised and traumatised. He spent upwards of a couple of hours in the vehicle waiting to be cut out."
The digger was driven out of a locked compound adjoining the 34,000-acre firing range as police were escorting protesters down the hill from the main entrance, where they had gathered for two nights.
It collided with a military checkpoint before clipping vehicles, including one belonging to a protester, and striking the police van. It then disappeared down the track before turning on to the A40.
Policeyesterday dismissed claims from some protesters that the alleged driver was an MoD employee. It is not known whether any of those detained were linked with the demonstrations.
Meanwhile, organisers of the protest, who claim the use of the firing range could lead to the infection of animals on surrounding land by contaminating streams, called off their blockade.
Mr Powell said: "I feel deep, deep sadness and immeasurable sorrow. This incident has soured everything. It pains me that all the good work of people should have been destroyed in this way."