POLICE are investigating whether a phenomena dreaded by caravanners known as "the tail wagging the dog" was to blame for the death of Marine Commando William Priddy on the Burbage bypass on Monday.

The 21-year-old lance bombardier, a member of the Royal Marines 29 Commando based in Plymouth, was killed when the Land Rover he was driving flipped over onto its roof.

It is understood that he was not wearing a seat belt. The only other occupant of the vehicle, another young Marine, was wearing a seat belt and was uninjured.

Police said the Land Rover was part of a convoy of eight military vehicles travelling on the A346 Marlborough to Salisbury Road, heading towards Salisbury Plain for a exercise.

At a point about 400 metres north of the Seymour Pond roundabout at the southern end of the by pass the Land Rover began to overtake a grey Audi A4.

The Land Rover was towing a heavy trailer and police are investigating the possibility that as the vehicle built up speed the trailer began to waggle.

This is a phenomenon feared by the drivers of tow vehicles because it can lead to the trailer snaking to such an extent that it flips the tow vehicle onto its roof.

Haynes Complete Caravan Book of Advice for new caravanners warns that unless snaking is controlled "taking the wrong action too late could lead to a serious accident".

The manual states: "What starts as a gentle swaying from side to side at the rear of the caravan builds, sometimes quite suddenly, into a fierce pendulum effect.

"The rear of the caravan swerves from side to side so strongly that what usually happens is that the car loses control and is swung across the road by the movement of the caravan.

"This is known as the tail wagging the dog."

Witnesses told police that as the Land Rover and trailer built up speed to overtake the Audi, the Marine driver lost control.

The Land Rover hit the grass bank on its nearside, clipped a tree and flipped onto its roof.

The front offside corner of the roof took the full force of the vehicle crashing back onto the road and collapsed, causing the driver severe head injuries.

He was certified dead at the scene and the road was closed from shortly before 5pm, when the accident happened, until about 8.30pm while officers from Salisbury traffic unit carried out an investigation.

Police operated diversions through Burbage village.

The driver's details were released yesterday and although police did not give a home address, officers said he was not from Wiltshire.

It is understood Lance Bombardier Priddy was based at Plymouth.

The Wiltshire coroner, David Masters, was informed of the tragedy and will be conducting an inquest.

The Burbage by pass opened in 1991 after more than 30 years of campaigning by villagers about the heavy holiday and commercial south coast traffic.

Original plans were for the bypass to include the notorious skew bridges north of Burbage and the Mar Green bends south of the village that have claimed numerous victims.

Parish council chairman John Powell said he believed Monday's tragedy was the first fatal accident to occur on the bypass in 14 years.