Two soldiers fatally wounded after an explosion and fire on their tank at an Army live-firing range died after a design flaw went undetected on their armoured vehicle’s gun barrel, a coroner has concluded.

Corporals Matthew Hatfield and Darren Neilson, both of the Royal Tank Regiment (RTR), died of their injuries after an incident on their Challenger 2 at the Castlemartin firing ranges, Pembrokeshire, Wales, on June 14 2017.

Louise Hunt, senior coroner for Birmingham and Solihull, said the “main cause” was that the gun could be fired when a key component – the bolt vent axial (BVA), which forms an air-tight seal blocking hot gases escaping into the crew turret – was missing.

She said: “The main cause of this incident was the tank being able to fire without the BVA assembly being present.”

Ms Hunt added: “During production and manufacture of the gun, this hazard was not adequately considered or investigated and therefore the ability of the gun to fire without the BVA present … went undetected.”

Castlemartin inquest
Corporal Matthew Hatfield, pictured here with daughter Lexi, who died alongside Corporal Darren Neilson (Abigail Hatfield/PA)

Ms Hunt added that there were “other issues which contributed to the incident” including a lack of written processes and procedures for soldiers to follow, when handling the BVA, handing over tanks to new crews, communication, and equipment drills.

Ms Hunt was delivering her conclusions following an inquest which heard how the BVA air-tight seal stopping 3,000C high-explosive gases escaping into a tank crew’s turret was not in place before a lethal blast.

There was no set system in place to check for the key piece of equipment – the BVA – and an unknown loophole in the tank’s gunnery system meant it could be fired when not present.

The inquest also heard that four of tank’s high explosive ammunition bags, known as “bag charges”, which propel the shell out of the tank’s barrel, were “incorrectly stowed”.

Ms Hunt concluded: “Failure to correctly stow charges caused a secondary explosion following failure of the breech block due to the absence of the BVA assembly, and the practice of un-stowed charges was routine.”

The coroner heard a succession of troopers give evidence that the charges were sometimes stored out of heat-proof storage bins within the turret, including an occasion where one was “on a soldier’s lap”.

Castlemartin inquest
Corporal Darren Neilson, of the Royal Tank Regiment, and Cpl Hatfield were both veterans of Afghanistan and Iraq (Jemma Neilson/PA)

Cpl Neilson, 31, a father-of-one from Preston, Lancashire, was the tank commander and was thrown from the turret during the blast, while Cpl Hatfield, 27, and also a father, from Amesbury, Wiltshire, was loading ammunition.

Both men were evacuated from the scene but later died of their injuries.

Two other soldiers, Warrant Officer Stuart Lawson and Trooper Michael Warren, were also injured but survived.

Cpls Neilson and Hatfield, both highly-trained gunnery instructors with combat experience in Iraq and Afghanistan, were taking WO Lawson out for a “guest shoot” experience, to show how the tank performed when firing.

Castlemartin inquest
Warrant Officer Stuart Lawson, who survived the explosion that killed the two soldiers (Joe Giddens/PA)

But the inquest heard the RTR commanding officer Lt Col Simon Ridgway was supposed to have written authorisation from a more senior officer for the guest shoot, as required by Army rules, but told the coroner he “had not appreciated that at the time”.

He also “failed” to spot a culture of crews wrongly storing high explosive charges in their turrets.

Asked if it was a failure of his leadership during his evidence, Lt Col Ridgway said: “I think I failed to identify it was happening.

“I’m not sure it’s a failure of leadership.”

Battle of Cambrai centenary
Lt Col Simon Ridgway, RTR’s commanding officer, pictured at its HQ in Tidworth, said he felt “physically sick” at the thought of incorrectly stowed bag charges (Ben Birchall/PA)

He added: “I have to admit I sort of felt physically sick when I heard people were stowing them out of the bins.

“If for one moment I suspected they were storing them incorrectly, I would have been furious.”

It also emerged Lt Col Ridgway – a veteran of the 2003 Iraq invasion – did not know the guest shoot was happening that day, and had not passed down his order for Mr Lawson to “sit on his hands”, and leave firing to the tank’s commander.

The inquest also heard how crews shared tanks, known as “hot-bedding”, but that a simple whiteboard – used to assign crews and activities to tanks – was not always updated promptly.

The Army told the coroner it has tightened training and drills since the incident.

A report to prevent future deaths with three recommendations has been sent to the Ministry of Defence and BAE Systems, which designed and manufactured the Army’s main battle tank.