Navigating his way through the treacherous Khumbu Icefall on the slopes of Mount Everest, listening to ominous rumbles overhead, Karl Hinett admits that he was as scared as he’d ever been. “It’s like walking through a moving river of ice and there’s a huge avalanche risk,” he recalls. “It’s where most of the accidents happen on the mountain. It was pitch black and I was extremely scared. It was a very long night.”

Nor does the 25-year-old frighten easily. Seven years ago, aged just 18, Karl was seriously injured when his Warrior tank received a direct hit from a petrol bomb as he patrolled in Basra. The moment he managed to clamber out, engulfed in flames, was captured by a photographer and became one of the defining images of the conflict.

With severe burns to his arms, legs, hands and face, Karl thought he would never live a normal life again – yet this year, he joined a team of five wounded soldiers taking on the challenge of climbing Everest, an expedition that follows on from a similar trip to the North Pole last year.

Both missions, organised by soldiers’ charity Walking with the Wounded, were accompanied by documentary cameras, which recorded the expedition’s highs and lows, both physical and emotional. There was an abundance of both as the team battled sub-zero temperatures, night climbs and ladder crossings over deep crevasses - all against a backdrop of mounting fatalities on a mountain that has seen its second highest death toll during this year’s climbing season.

Everest, of course, is a monumental challenge for even the fit and able-bodied, quite aside from soldiers with missing limbs and, in Karl’s case, extensive burns. “From the start everyone who was taking part was made well aware of the sort of conditions we’d be in and the fact that able-bodied people struggled. We knew what we were undertaking,” he says. “At the same time in our eyes we’re pretty normal – we don’t really see each other as disabled.”

Karl, from Tipton in the West Midlands, underwent 100 hours of surgery but has adapted to his burns, and, by and large, manages with everyday life, though his hands, which were most badly damaged, tend to struggle with fine dexterous movements. “I had to be swathed in huge amounts of cream and face masks and specialist gloves to make sure my skin didn’t get exposed, as it burns really easily – particularly at altitude.”

Prior to departure there were months of arduous training, on occasions with royal support; as patron of Walking with the Wounded Prince Harry paid several visits to the would-be mountaineers. The Prince says: “For someone like Karl, to have to get over the experience that you’ve had and the horrible place that you’ve been. You have to have a very strong head to carry on with life.”

The group arrived in Nepal at the end of March before trekking to Everest Base Camp, and hoped to reach the mountain’s summit, 8,848m above sea level, by the end of May. Each day got a little harder. “It was demanding mentally and physically. We all struggled with the altitude and sometimes I’d wake up shivering from the cold. There were days when just putting one foot in front of the other would be exhausting.”

His damaged hands, meanwhile, were a particular issue. “The cold made them stiffen up so much that my nails would break off. I spent a lot of time having them super-glued back on. But it never occurred to any of us to turn back.”

Sadly that decision was made for them: shortly before their push to the summit, seven weeks into their trek, the expedition leader called off the trip. “We were preparing for the final push to the summit when we were told it was too risky because of falling ice and an increased avalanche risk. We were gutted because we were so close but we totally understood and respected the decision. And it was the right decision because after we left people still tried to summit and unfortunately lost their lives. Yes, it was frustrating but reaching the top was only one part of the challenge; we were there to raise money for wounded soldiers. We all saw that as our main role.”

It’s a role that has almost become a way of life for Karl. Since being injured, he has raised thousands of pounds for charity, especially the Queen Elizabeth Hospital in Birmingham where he was treated. Last year he ran 52 marathons and he’s a third of the way through running an equal number this year. Is this his way of redefining himself?

“I think I’m just more inclined to see how far I can push this body I’ve been given,” he says. “It wasn’t my choice, but it happened. I realised very early on when I was lying injured in hospital, bed-bound with no independence, that I would have to build myself up from where I was. And each time I’ve achieved something it’s pushed me to do something more. There has never been a point where I thought, ‘This is it, that’s the end, I can‘t do anything more’.”

He admits he harboured dreams of returning to the Army, but realised that doing so would potentially compromise his colleagues. "I could still handle a rifle, but it would be in my own time and I’d never want to get to a point where that extra few seconds would be putting someone else’s life in jeopardy. Once I saw it that way I was completely happy.”

In fact he is remarkably free of bitterness or anger. “Looking at that photo doesn’t upset me, it doesn’t bring sadness. The memory of that day is crystal clear, but in some ways it’s like it happened to someone else. I’m just glad I have got where I am.”

He feels the same way about Everest. “Seven years ago, as I was lying in my hospital bed I could never have imagined anything like it. Just to say I’ve been there, that’s special in itself. It was a long way from where I’ve come from.” 

Harry's Mountain Heroes is on Monday at 9pm on ITV1