The family of a Royal Marine from Watford, killed in Afghanistan, has thanked his fellow soldiers for trying to save his life.

Corporal Christopher Harrison, 26, was leading a patrol when an improvised explosive device (IED) blew up near Sangin, Helmand Province, on May 9, 2010.

An inquest at Hatfield Coroner's Court on Wednesday heard the Royal Marine, from 40 Commando, was “unlawfully killed” when he suffered "non-survivable" injuries in the explosion, which injured two other men.

Despite this, however, soldiers in his troop immediately gave him first aid and called for emergency medical help before he was evacuated from the area by helicopter.

Martin Harrison, Cpl Harrison’s father, from North Western Avenue, Watford, said: “On behalf of the Harrison family I would like to confirm our satisfaction at the coroner's verdict and thank him for conducting the inquest in a way that noted Chris's good humor and wonderful character whilst giving testimony to the high regard in which he was held by his Royal Marine contemporaries.

“We wish to commend the efforts of both Chris's Royal Marines patrol comrades and the emergency medical team who attempted to resuscitate him whilst under fire in extremely hostile territory in Sangin district. We are satisfied that everything possible was done to try to save his life.

“We would especially like to thank from the heart Chris's good friend and comrade Marine Marc Bird for his valiant attempts to revive Chris and tend his injuries whilst awaiting the medical team's arrival. It must have been extremely difficult for somebody to deal with that situation involving a close friend.

“We remain devastated by Chris's untimely death in the ambush and miss his presence in our lives sorely. We think about him all the time.

“We will always be immensely proud of his bravery and the achievements in his all-too-short adventure of a life.”

Mr Harrison and Cpl Harrison’s brother Russell and wife Rebecca were in court to hear evidence from three marines, two of whom were part of the patrol he was leading that day.

The inquest heard that as part of an early morning mission on May 9, Cpl Harrison, a mortar fire patroller, was made command leader of one of four troops sent to provide protection to soldiers establishing a vehicle check-point on a main road.

Major Mark Totten, of 40 Commando, said: “Because of his ability as a commander and as a marine, I was confident to use him in a role commanding a section on the ground. He was a very capable leader. He had my confidence he could lead a section.”

While moving towards their destination, Cpl Harrison reported to Major Totten that his troop were moving into position but were having difficulty crossing the high compound walls on their route through a densely built-up area.

Major Totten told the inquest: “Just after he let me know that was the case, I heard and saw a large explosion.”

Marines Ross Patterson and Ben Wade were sweeping the troop’s path for improvised explosive devices before the bomb hidden in the wall four feet from the ground detonated; the latter suffering shrapnel wounds to his face.

Marine Patterson, who was standing one metre in front of Cpl Harrison, told the court: “When the explosion went off, I fell forward. When the dust settled, I found a hole 2.5m wide in the wall opposite. Then I saw Chris who was quite close.

“I gave first aid but couldn’t do anything for him.”

Fellow marine Marc Bird said: “It knocked the majority of the patrol over. I looked up and saw a giant cloud of black smoke. I saw Chris lying on the ground against a mound of rubble. I tried to pick him up but I couldn’t. I shouted around to the guys and they came round. We were able to get him on a stretcher.”

Major Totten described Cpl Harrison as an “exceptional Royal Marine junior leader”.

“He was very committed to his profession, very proud of his profession,” he said. “His commitment is highlighted by manner in which he volunteered for this operation and wanted to be a section commander and Royal Marine commander.

“Outside his professional life, he was one of the most humorous, engaging and fun loving people the core had and he was a real treasure for us.”

Coroner Edward Thomas ruled that Cpl Harrison was killed unlawfully in active service.

"He was obviously a first class person,” he said. “A lot of people clearly had a lot of respect for him and he was described as exceptionally good at his job.

"But he also was a lovely man with an infectious sense of humour and somebody who will always be remembered with great affection."