A teenage Warminster-based soldier killed alongside five colleagues in a bomb blast in Afghanistan had taken the place of a fellow private at the last minute, an inquest heard yestereday.

Private Christopher Kershaw volunteered to take the place of another soldier as the driver of a Warrior armoured vehicle which was blown up just minutes later during a patrol in March last year.

The 19-year-old died alongside Sergeant Nigel Coupe, 33, Corporal Jake Hartley, 20, and Privates Anthony Frampton, 20, Daniel Wade, 20, and Daniel Wilford, 21, during the incident in Helmand Province on March 6 2012.

An inquest into their deaths at Oxford Coroner's Court yesterday heard that it was most likely that Sgt Coupe, a member of 1st Battalion The Duke of Lancaster's Regiment, and his comrades, all members of The Yorkshire Regiment's 3rd Battalion, were either killed or knocked unconscious by the huge blast, and unaware of what happened afterwards.

The Warrior, known by the callsign K12, was patrolling with another vehicle when it was hit by an improvised explosive device about 25 miles north of the capital of Helmand, Lashkar Gah.

The force of the explosion turned the it upside down and blew off its gun turret. Ammunition on board the vehicle ignited, causing a fierce fire.

The attack, the deadliest single enemy attack on UK forces in Afghanistan since 2001, was claimed by the Taliban at the time.

The inquest heard that the patrol was meant to leave earlier that day but was delayed because of a sandstorm. It eventually left just after 6.30pm, and was blown up minutes later.

Fellow soldiers in a second Warrior vehicle, given the callsign K13, reported hearing an explosion then seeing a "fireball" as it ignited.

In a statement read to the court, Private Luke Stones, of 3 Yorks, described how Pte Kershaw - who was driving the Warrior - had volunteered to take the place of another soldier on the patrol.

"Private Butler would have been the driver of K12 but he was returning from the shower and as a result Pte Kershaw offered to take his place," he said.

Pte Stones, the gunner in the second Warrior, said he heard a "large explosion" just five minutes after leaving the base.

"Around 20m to my front was a large fireball which had flames reaching around it," he said. "I stood staring at the fireball not really understanding what I was looking at."

The blast had blown the armoured vehicle on to its side, and blew its gun turret off, the inquest heard.

The inquest heard that all six men died of blast injuries caused by the explosion. Reports from two pathologists said it was most likely that all six were either killed or rendered unconscious by the blast, leaving them unaware of what happened afterwards.

The inquest heard that an intelligence briefing was given to troops earlier that day, which had included Pte Kershaw despite his late addition to the patrol.

Intelligence officer Staff Sergeant Scot Cooper told the inquest that the IED threat at that time in the area was low.

Father-of-two Sgt Coupe, from Lytham St Annes, Lancashire; Pte Wade, from Warrington, Cheshire, who was about to become a father; Cpl Hartley, from Dewsbury, West Yorkshire; Pte Frampton and Pte Wilford, both from Huddersfield, West Yorkshire, and Pte Kershaw, from Bradford, had all only been in Afghanistan for a few weeks.

The tragedy was, and remains, the biggest single loss of life for British forces in Afghanistan since an RAF Nimrod crash killed 14 people in September 2006.

Major Edward Colver, responsible for running the Patrol Base called Lashkar Gah Durai, said three patrols were due to go out that day - one foot patrol; one administrative patrol in vehicles going to another patrol base, which was cancelled because it was not needed; and a third "ground domination area" (GDA) patrol, which was due to go out at 4pm but was delayed due to a sandstorm.

Maj Colver said that later, when he was deciding whether to send the patrol, he looked out of one of the guard towers and could see "pretty much as far as my eye could see".

Asked if he had any concerns about visibility, he said: "None whatsoever. And, as a commander, if I had any concerns, I could not get a helicopter in because visibility was so low I would not have sent a patrol out."

He said it was "standard operating procedure" to try to send a patrol out after a period of not being able to see what was going on.

"When you have that drop in capability, that drop in 'eyes on', you send out patrols," he told the inquest.

"Projecting your force keeps the enemy on the back foot, it keeps them from knocking on our door."

He said the patrol left at 6.32pm, and was only due to last 20-30 minutes.

Maj Colver said soldiers were taught to look for "groundsign" - signs of possible IEDs - but it was difficult because of the terrain, which he compared to the surface of the Moon, and dust thrown up by the vehicle.

The inquest heard that, after the tragedy on March 6 2012, Maj Colver's company suffered seven IED hits on Warriors during the tour, including one only a week later.

But he said the damage in the other incidents was fairly similar, including blowing the track and road wheels off the vehicles.

"In many cases the integrity of the turret, the crew compartment and the driver's hatch remained," he said, adding that in those cases soldiers suffered minor injuries such as shrapnel wounds, but nothing serious.

Asked by lawyer Michael Davison, representing members of three of the families, why he had decided to send out the patrol at that time and not the following day, he said: "Force protection - the insurgents seeing that we're out.

"You have to constantly keep the insurgents on the back foot. We hadn't been out from the morning until late afternoon.

"If I hadn't sent that patrol out, we wouldn't have had anyone out for around 20 hours. I deemed that too long."

Asked why Pte Butler was in the shower yet Pte Kershaw was ready, despite not being due to go on patrol, he said he did not know the details of different soldiers' washing schedules but said of Pte Kershaw: "being a good bloke, he stepped up to the mark".

The inquest was due to resume goday.