Two young men stood nose to nose on a south London street a few months ago, in a furious argument over a minor car accident so heated it had to be broken up by police.

The scene would have been utterly common place, banal even, had one of the young men involved not been the country's greatest living war hero – Victoria Cross recipient Lance Corporal Johnson Beharry.

"I actually wanted to kill the person. The police had to come," explained the 29-year-old, who is one of only 10 living VC holders. "It was not about the car, it was not about the accident. I have been told that because of what happened to me [in Iraq] all my body can remember is defence. Any time something happens I go into a defence mode."

Download the new Independent Premium app Sharing the full story, not just the headlines

Cpl Beharry's gentle face is now familiar across the country. He is the quiet, solemn figure who stood behind 110-year-old veteran Harry Patch on Armistice Day. Since becoming the first living recipient of a VC for 40 years for "repeated extreme gallantry and unquestioned valour", the young Grenadian has been portrayed, somewhat patronisingly, as a humble, almost docile Caribbean soldier.

Cpl Beharry is a confident, self-possessed, yet modest, man, driven to make something of his life and help others. But he is also a soldier tortured by mental and physical wounds, who has had to learn to live with constant pain, nightmares, mood swings and unexplained rages. He has decided to speak out for the first time on behalf of the thousands of servicemen and women suffering in the UK, who are forced to turn to charities for help because the Government is failing them.

The soldier cannot remember the last time he had a good night's sleep. Almost five years after he saved the lives of 30 comrades in Iraq by driving through a series of ambushes – his head sticking out of the burning Warrior armoured vehicle "despite a harrowing weight of incoming fire" – he can get no rest.

"If I fall asleep, I relive all the contacts [battles]. I start sweating. Even thinking about it now I am beginning to sweat," he explained. "Kosovo, Northern Ireland, Iraq, training – it all blends into one. One minute, I will be in Iraq on top of a building and the next thing I am in Grenada with my friends during the same contact. I have been told I kick in my sleep and worse. I used to get a couple of hours a night but recently, I can't sleep again. I lie there at night, tossing and turning. I put on the TV. I try to read to get tired but I can't. You think the next night you are so tired you will sleep but you don't."

The rocket-propelled grenade that tore open his skull put him in a coma for eight days but, Cpl Beharry explained in an unemotional tone, he survived because his head was so smashed up that it allowed room for his swelling brain. Today, his hair has largely grown over the scar which extends from one ear to the other. But the pain persists, jumping from his back to his shoulder and bouncing around in his head. He likened it to an agonising toothache but he refuses to take painkillers for fear of becoming dependent.

"No one expected me to walk or talk or even be alive. My mind is telling me everything is fine and my body is reminding me it is not. I have been told it is memory pain, the body catching up. My psychotherapist explained that the body could only deal with a certain amount of pain at a time so it comes out later. When I get those moments, I get angry."

Ironically, he chose to endure more pain when he decided to have the Victoria Cross tattooed across his entire back. It is a reminder that he his not just a man who will go down in history for his bravery but an ordinary young soldier with the customary penchant for the artist's needle.

Daily coronavirus briefing No hype, just the advice and analysis you need Enter your email address Continue Continue Please enter an email address Email address is invalid Fill out this field Email address is invalid Email already exists. Log in to update your newsletter preferences Register with your social account or click here to log in I would like to receive morning headlines Monday - Friday plus breaking news alerts by email Update newsletter preferences

On his uninjured shoulder is a tattoo of his late grandmother, to whom he would run as a child when his father was violently abusive, and who instilled in him values, aspirations, and a respect for religion. The body art represents the most important things in his life alongside his fiancée, Tamara Vincent.

The boy who walked to school barefoot speaks with informal ease of meeting royalty and heads of state. When he was presented to the then US President, George Bush, before the election, he boldly asked him who he thought would win. Bush replied "Obama". When Cpl Beharry met the Queen on his investiture at the Palace, she said to him that it was the injuries people could not see that would take the longest to heal. The combination of brain injuries and combat stress has made an angry young man of him at times, often completely irrational, he said. During his time in Amarah with the 1st Battalion, The Princess of Wales's Royal Regiment, his battle group came under attack more than 800 times.

"People don't realise how hard it is for soldiers. You spend six months on the battlefield and you have to defend yourself every day and then you come back to normal life and go to Tesco's and someone runs into your trolley. You have to stop and think it is only a trolley, you are not on the battlefield. We are trained to be angry. We are trained to kill and then at five o'clock you have to go home, adjust, change completely to a different person. You can't react the same way." He continued: "The only people who can relate to it is other soldiers or ex-soldiers who have been through the same. I find it difficult to talk to normal civilians."

The wail of a siren, the bang of a door, any loud noise, reminds him of the RPGs that blasted into the Warrior armoured vehicle he was driving, of the day he repeatedly leapt on to the burning vehicle to drag injured colleagues to safety, or the moment six weeks later when he was injured again, this time almost fatally. "It brings me back into the killing zone, to the explosion. When you hear a bang in Iraq, you know it is going to be followed by something and back home you still feel the same. You go tense, waiting. I go into that defence mode. Everyone experiences combat stress differently. But we are all linked.

"The guys are dealing with it in their own way," he added. "A lot of soldiers who were there in Telic 4 [the Iraq campaign of summer 2004] have left the Army. Those who are still serving get some form of help for combat stress, but not enough."

War veterans are supposed to get priority treatment in the health system for conditions resulting from military service but many complain that the reality is very different. "It is disgraceful that an ex-serviceman or woman has to go to the NHS. The Government should have something in place," he said. "I don't think the Government is doing enough for soldiers, personally. That is why you have all these different organisations like Help for Heroes."

The burden of the VC has placed incredible pressure to be a "superman". "I am no different to anyone else. I did something out of the ordinary but I hope that someone else would have done the same thing in my position. There is a lot of stress. The hardest part of it is so much is expected of me. I now have to carry myself in a certain manner and it is hard work."

His brain injury has also left him with a terrible short-term memory. "If people can see the problem, maybe they can sympathise, but when they can't it is very difficult. People see me acting normally but inside I am dealing with the pain of the injury." But he added: "I worry something is going to happen to me, that one day my injury is going to creep up on me and I will be in bed all the time."

While he is grateful for all the care he has received, he worries for others. "Two years ago, I went to King's College Hospital because I was in so much pain. I sat in the waiting room for three hours before I could see a doctor. It was ridiculous. It is not because of who I am that I should be treated first. I think all soldiers should be treated equally.

"Ex-servicemen and women should get the treatment but they don't get it. We need to raise awareness in the NHS. These are people who have served this country. Why can't they get treatment?"

Sitting in a smart London hotel, he is all too aware that many of his regiment are in Iraq and Afghanistan and, like VC recipients before him, he will never return to the frontline. He is deeply frustrated by the enforced inactivity, unable to join his regiment and desperate for the Army to find him a role. "I don't regret anything that happened to me but I feel like I am 60 years old because I don't have a job. I am employed but I don't feel employed. I want to achieve something in life."

Four years after being awarded the VC, he lives in a small house on a quiet south London street, living off a Lance Corporal's salary, boosted by a reported £1m book deal. He is sanguine about the press coverage which followed his split from his wife, Lynthia, days after the investiture. "Everything about me is in the open. I have nothing to hide," he said. He spends his time promoting his book, Barefoot Soldier, which describes his early days growing up in an impoverished Caribbean family, his move to the UK at 19 and decision to join the Army – and pursuing his passion to inspire children from difficult backgrounds. "Because I was involved in drink and smoking weed, I can say I was there and look at how my life turned around, tell them they have a choice: a job or prison."

He also helps out with countless charities, including Combat Stress, which offers a lifeline to thousands of servicemen dealing with mental health problems. The charity has experienced a 53 per cent increase in the past three years in veterans presenting with post-traumatic stress or complications brought on by combat. A £4m grant from the Ministry of Defence covers less than half its costs, and it must rely on other donations. A portrait of Cpl Beharry is among items being auctioned at Combat Stress's 90th anniversary ball, organised by another decorated former soldier, Kevin Godlington, in London on 11 June.

But while Cpl Beharry is happy to put himself in the public eye to help such causes, he finds attention difficult and rarely takes public transport.

With a wistful grin he explained: "Eric Wilson [the country's oldest VC holder, who died last year aged 96] said to me 'Young man, your life will never be the same again.' At the time, I thought it was just a saying but, trust me, it is not."

The 90th Anniversary Ball for Combat Stress is being held on 11 June at the Berkeley Hotel in London. Tickets are available from Robert Marsh at Combat Stress by telephone: 01372 841615; email: robert.marsh@combatstress.org.uk; or through the website: www.combatstress.org.uk. Donations can also be made at the Matterhorn Challenge Team website www.matterhornchallenge2009.org.

Medal-winning heroism: 'Extreme gallantry and unquestioned valour'

An edited extract of the VC citation for L/Cpl Beharry, then a private

Private Beharry carried out two acts of great heroism which saved the lives of his comrades under intense enemy fire and at great personal risk to himself.

On 1 May 2004, Beharry's company was ordered to replenish an outpost in the city of al-Amarah. He was the driver of the platoon commander's Warrior armoured fighting vehicle.

As his platoon passed a roundabout, they saw the road in front was empty. The platoon commander ordered the vehicle to halt. It was hit by multiple rocket-propelled grenades (RPG).

The platoon commander and the vehicle's gunner were incapacitated and a number of the soldiers were also wounded. Beharry closed his hatch and moved toward a barricade. The vehicle was hit again by RPGs. He drove his Warrior through the barricade. By doing this, he led the remaining five Warriors behind him towards safety.

Another RPG destroyed his periscope, so he was forced to drive with his head exposed. The vehicle was again hit by RPGs and small arms fire. He was hit by a bullet, which lodged on his helmet's inner surface. He continued to push through the extended ambush until he broke clean.

On 11 June 2004, Beharry's Warrior was part of an attempt to cut off a mortar team in al-Amarah. He was moving towards the suspected firing point when his vehicle was ambushed. A RPG detonated six inches from his head. Other rockets hit the vehicle, incapacitating his commander and injuring several of the crew. Beharry reversed the Warrior out until it hit a wall. Beharry then lost consciousness. By moving the vehicle he enabled other Warrior crews to extract his crew.

Despite receiving a serious head injury, his level-headed actions almost certainly saved the lives of his crew. Beharry displayed repeated extreme gallantry and unquestioned valour in the face of relentless enemy action.