At first light, Rob Long left a British Army base in Helmand province, setting out on another covert mission with his team.

He and the rest of his specially trained unit was to go behind enemy lines in Afghanistan’s Sangin area, where “1,000 explosive devices were being laid each month”.

"As we got to the target zone, the sun was starting to rise," Rob recalls. "It was the last sunrise I ever saw."

The patrol commander, bombardier Sam Robinson, had slipped and set off a concealed bomb, dying instantly.

Rob, meanwhile, was blinded by the blast from the improvised explosive device (IED). He was just 23. One of his eyes was “eviscerated” – while the other was removed by doctors shortly afterwards.

Twelve years later, the former serviceman navigates his way around his cottage on the outskirts of Canterbury through a combination of touch and memory. And where his eyes once were are two acrylic replicas.

“I’d gone from being a frontline soldier at the sharp end in an elite unit to having to hold someone’s hand to go down the street,” the 34-year-old says. “I wasn’t able to do the job I loved anymore, and it was really tough for me.

“In that area of Sangin, Helmand province, it felt like the ground could explode at any point. Roughly every other day there was a guy being killed or maimed from the British Army alone.

“That was the big threat out there. I was close enough that my left eye got ripped out on the battlefield – the medical report said it had been ‘eviscerated’ – and the other had to be removed.”

We're talking inside Rob's living room. When he opened the door to me, he turned and ducked underneath a beam as he showed me inside his rural home.

"The first few weeks - whenever the postman rang - I got a few head injuries and I was considering wearing a helmet around the house," he laughs.

"I use my phone a lot - it's amazing. I'll take a photo of something and it'll say what's in front of me - a human, dog, can of beans. It makes sure I've got paprika in my hand rather than cayenne pepper."

As he recounts tales of his truncated stint in the army, a smile spreads across his face.

Rob was just 19 when he signed up. The soldier was one of 58 servicemen who applied to join the special observation battery – a team that specialised in surveillance and target acquisition.

The teen lined up alongside snipers and commandos, as they began their first round of tests. These comprised five weeks of 30km hill exercises near the Scottish border, during which the hopefuls hiked to target locations through heavy rain and unforgiving terrain using just a compass and a map.

Rob counted his steps, knowing each one took him a metre forwards, until he reached the checkpoints. By the end of the five weeks, there were just 11 applicants remaining.

“After that we were split into two patrols. We’d step out at sundown and walk anywhere between 30km and 50km across mountains to get to a target point before first light, with 120lbs of equipment on our backs,” he remembers.

"As we got to the target zone, the sun was starting to rise. It was the last sunrise I ever saw..."

“Once you get to your target, you have to conceal yourself before the light comes up – and during the day you can’t move. People will be walking past you and shouldn’t be able to see or smell you.

“In these concealed areas you can’t leave any trace, so you’d have certain techniques for keeping urine and excrement with you – you have to keep it all in your bag. We were facing the Taliban, and you didn’t want to be captured. You can’t stop the war to go to the toilet.

“We were training to be in close-target surveillance and target acquisition. This meant we’d find the enemy, monitor troop movements and had a find-and-finish capability.”

In all, just eight people passed the course. But it was not until several months later that Rob was sent out on his first – and only – tour overseas. He was called into his sergeant major’s office and informed that an opportunity had arisen in Helmand province.

He was to set off just in a matter of weeks for the 10-month job. Stony-faced, Rob’s boss warned him it was a role that was prone to capture and involved patrolling “IED-infested areas”.

“It was the best job I could have got in the unit. It was what I had trained for,” he says.

After landing in Kabul, he was sent to Camp Bastion to acclimatise to his new surroundings for a fortnight. The nine-man team hashed out which ally base it would go to first, all the while dead and mutilated soldiers were rushed into the medical tent next door “four or five times a day”.

When they left for Sangin, their time was filled with night-time covert patrols. They would also erect armoured cameras – which were conspicuously placed “so locals knew the area was being monitored” – along previously unsafe routes.

The team provided much-needed help to secluded bases, which would “sometimes just be a house with three or four British Army troops inside”. While carrying out these tasks, Rob encountered nearby residents and farmers – many of whom carried AK47s.

He and his eight pals had been shot at, experienced “close calls” and had been forced into firefights with Taliban forces – but they were yet to suffer an injury. That changed on July 8, 2010 – just four months into the mission.

“It was a covert operation," Rob recalls. "I remember we were in the target area, and then there were just flashes of the IED. Sam Robinson was killed straight away. My left eye had been smashed out of my head, I had burn injuries, a dislocated shoulder and my right eye wasn’t very good at all.

“Our unit had split up, and this left us with one guy dead and two severely injured – so there were only two guys left and we were inside enemy territory. Our intelligence said 1,000 IEDs were being laid each month in Sangin alone – that was just one part of Helmand province.”

Despite this, Rob was flown back to the UK less than 24 hours after the blast. He regained consciousness in an intensive care unit in Birmingham, where he was flanked by a seriously injured Ghurka and a member of the SAS. The three of them were all wired up to life-support machines.

His face was swollen, with more than 100 fractures across his skull. Family members told him the only features of his that they recognised were his ears. Meanwhile, shrapnel was lodged underneath his skin.

“On top of the news that I was to lose my sight, I was told Sam was dead. I was just devastated,” Rob utters, his voice quiet. “I discharged myself after three weeks because I wanted to get to Sam’s funeral.

“We were brothers. We were spending every single second with each other. We knew everything about each other, and were in highly dangerous situations together.”

Later that year, Rob was contacted by Blind Veterans UK. The charity brought him to its centre in Brighton where he was taught how to use a cane and live independently. By this point, the former soldier would find himself overcome with fatigue after just five minutes of walking as his brain struggled to navigate a world that had been plunged into darkness.

The experience broadened his horizons. And soon afterwards, he took up Brazilian jiu-jitsu. He was a natural. By being in such close contact with his opponents, Rob was able to sense what they would do next without needing to look at them.

Within six months, he won heavyweight gold in a British Army competition against serving soldiers. He was the only injured veteran to take part. For three years, he was the number-one ranked parajiujitsu martial artist in Europe, and he has set himself the goal of becoming an able-bodied world champion.

• To follow Rob’s journey, visit his Instagram page here.

Having moved to Canterbury last year, he has now launched a bid to build a training facility in his back garden. Plans show the complex will be used once a month by as many as 15 injured former servicemen at a time to train during the day. Overnight they’ll camp out in five tents dotted around his grounds and share stories.

As part of the five-figure project, Rob also hopes to create wheelchair-accessible paths across his grounds. He currently navigates his way around his garden by following a series of ropes stretched around its perimeter.

“I want to do it on a shoestring budget. People from my unit are volunteering to help me with a lot of the labour because some of them have gone into the construction trade,” he explains.

“Jiu-jitsu gave me my life back and it gave me a huge part of my identity back. I was in the pits and felt like nothing at the time.

"Our unit helped save lives out in Afghanistan, and we did everything professionally. We saved Afghan and British lives, and helped the populations in those areas. I was incredibly proud of my job - I loved it.

"Doing jiu-jitsu meant the bomb blast wasn’t the life-altering moment I thought it was. I want the ability to bring that to other veterans who have suffered injuries.”