AN inquest resumed today into the death of Runcorn Col Sgt Martyn Horton who died in a car crash in Afghanistan.

The British armoured vehicle he was travelling in rolled into a canal in Afghanistan - killing four of its occupants - after colliding with an Afghan National Police car.

Col Sgt Horton, Lance Corporal David Ramsden, Private Douglas Halliday and Private Alex Isaac - all from the 1st Battalion The Mercian Regiment (Cheshire) - died in the incident.

The soldiers were members of a police advisory team and travelling as part of a two-vehicle convoy near Gereshk in Helmand province on June 23, 2010.

Their vehicle, a 20-tonne Ridgeback protected patrol vehicle (PPV), driven by Lce Cpl Ramsden, collided with a 2-tonne Afghan National Police car by the Nahr-e Bughra canal.

Salisbury Coroner's Court heard the "glancing" impact between the vehicles pushed the Ridgeback onto two wheels before it rolled into the water - landing upside down about 13 metres away.

Dr John Searle, a consultant in accident reconstruction, said: "In my opinion, the front left corner of the Ridgeback has gone at right angles with the front right corner of the Ranger.

"It was a glancing impact, an impact where the vehicle carries on and is not stopped by the impact.

"The Ranger is rotating anti-clockwise, the Ridgeback is rotating clockwise and it climbs up onto two wheels over the bonnet of the Ranger.

"These movements are happening at the same time. After that contact, the Ridgeback goes into the canal to land upside down."

Dr Searle said the tyres of the Ridgeback had a very high friction, which resulted in a "grabbing" effect on the Afghan National Police Ranger.

He said the visibility in the vehicle at the time of the collision would have been similar to a car driving in normal night-time conditions.

"The Afghan National Police Ranger is a dark object being seen against a dark background," he added.

The inquest heard that it is impossible to estimate the speed the Ridgeback was travelling before the collision, but it is thought to be above 30mph.

"From the physical evidence, I wouldn't say that you could rule out a high speed," Dr Searle said. "It could well be that it was travelling at a high speed."

The inquest, which resumed today after being adjourned in November last year, heard how the incident happened as the vehicle was travelling to police checkpoint five (CP5).

The Afghan National Police had asked the advisory team to return to CP5 on the evening of June 23 following an attack of three explosions and gunfire.

After passing over a bridge near CP5, the lead Ridgeback collided with the Afghan National Police vehicle at around 9.40pm.

A loud bang was heard followed by someone shouting "we're going in" as the Ridgeback rolled down a steep bank and into the canal.

Pte Michael Peers, who managed to escape from the submerged Ridgeback, said the occupants were wearing seatbelts and opened the back hatch near the water, as was recommended.

"I heard a loud bang which was like an explosion, I do not know where it came from or where it impacted if it did impact," he said.

"I felt the vehicle jolt and I thought it might be an IED. I felt the vehicle swerve then flip over on to its right hand side.

"The whole event lasted a couple of seconds or less. The vehicle then fell over on to its left side and submerged in the water, I didn't have time to take a breath."

Col Sgt Horton, aged 34, from Runcorn in Cheshire, joined the Army in 1992.

He served in Cyprus, the Falkland Islands, Belize and Kenya, and on operations in Northern Ireland, Iraq and Afghanistan.

Following his death, his sister Caroline paid tribute to the loving father, brother and son, saying: "He will be fondly missed by everyone he knew and sadly died doing the job he loved."

The inquest, which is expected to last for five days, continues.