When Christopher Bulstrode first inquired about joining the army there was laughter at the other end of the telephone.

For at 56 he was seeking to sign up at a time of life when others might be contemplating retirement. And did this well-meaning man really understand just how traumatic military service in Afghanistan can be at any age?

But trauma is something that Prof Bulstrode knows a great deal about, after years of work in the John Radcliffe Hospital’s emergency department.

It did not take the army very long to recognise that they had on the phone a man worth far more than his weight in gold — they had someone with the knowledge to save soldiers’ lives and treat the most severe of injuries.

Within a short time he was leaving behind his work teaching medical students in the JR’s busy accident and emergency department to learn some of the rudiments of army life at Sandhurst.

“I found myself there with all these 20-year-olds on a course, learning to polish boots and dismantle a rifle. But I survived that.”

But there would be far harder challenges ahead once he began a nine-month tour of Afghanistan as a major in the Territorial Army in the Helmand Province.

What was to have been a three-month stay was extended and, as well as treating casualties, his role was extended to restructuring healthcare services in Helmand and assessing conditions in refugee camps.

It turns out his Afghanistan adventure is all down to his wife, the prominent medical educator Dr Victoria Hunt.

Sensing his frustration with the endless committee meetings, she challenged him to find a new arena in which to practise medicine.

“We were sitting having a glass of wine one evening and she told me that I was becoming boring,” he recalled. “So she dared me to join the TA. And nobody dares me to do anything.”

His first job as a doctor after studying medicine at Oxford had been to work at a camp for Ethiopian refugees in Sudan for Oxfam. So he was well aware of the risks facing medical staff who go to work in a war zone.

As a man who has not been a stranger to peace demonstrations, he also knew that this time he would be in an army uniform himself, with the rank of major.

Once in Afghanistan, the Oxford orthopaedic professor found himself working for three months in the comparatively humble position of emergency senior house officer.

But the experience of working under pressure as the casualties began coming into the new £10m field hospital at Camp Bastion, a giant fortress created in Central Helmand, served to renew his enthusiasm for clinical medicine.

The horrific sights he saw at Bastion continued to haunt his sleep months after his return home to Stanton St John. He recalls an incident last Christmas when a young man arrived with both his legs and an arm blown off. At one point, hearing a groan, he quickly rushed to the soldier’s bedside.

“You know why he called out? It was to tell me he was angry because he’d spent £120 on a pair of trainers before he’d left home. Can you begin to imagine what it must have taken to make a joke under those circumstances, with his life changed forever? They are just incredible people.”

In the case of the seriously injured, the role of his team was to stabilise the condition of patients, so they could be flown home for definitive and long-term care. But this is not to suggest that the hospital conditions were in any way inadequate.

“The medical equipment that we were given in Afghanistan is second to none. No expense is spared to enable us to provide the best treatment.”

One ethical dilemma that he has continued to wrestle with is the extent to which priority should be given to British troops.

“As doctors we are supposed to treat people equally, friend and foe. But inevitably there is only a limited amount of resource available and, when treating injuries, time is of the essence. Should we treat enemy forces at all, when they may use precious resources, like O negative blood, that might have left us vulnerable when one of our troops is brought in wounded?”

He kept a diary during his time in Afghanistan, in which he grappled with some of the moral issues facing someone trained to save life.

“If we are going to treat those injured in the conflict what about those children injured by Russians years ago, or in a road traffic accident? No sooner do you draw the line, than another case appears which stretches our ability to be fair and humane beyond what we are capable of doing.

“We can resuscitate an Afghan soldier rendered paraplegic by a bullet through the spine, but then what? There are no facilities for paraplegics in Afghanistan. He cannot stay in our hospital because we need the bed for the next acutely injured patient. However, when we discharge him, it is surely to a slow, lingering and avoidable death.

“What do we do with little girls mutilated by mines whose parents will now not take them back because they are too scarred to marry and therefore worth nothing? Do we send them out to starve? Everywhere you turn, the best intentions are perverted by the profound difference between our standards and values, until you feel paralysed by moral dilemmas.”

In his diary, he also analysed with typical honesty the reasons he and the other doctors had chosen to work in Afghanistan in the first place.

“I suppose that there is a little bit of a romantic in all of us,” he wrote. “For boys like me it was the dream that we might have a chance to do something heroic. Way back in those days when we read the Eagle Annual and the Boy’s Own comic, doing something important and brave was all so nearly possible — just around the corner when we had grown up a bit.

“As adults we all realised sooner or later that from now on we are going to be living humdrum lives — a quiet meander down to the muddy delta of retirement. But the Territorial Army offers the chance once more to come within grasping distance of those boyhood dreams. Suddenly we are transported out of our ordinary lives into places where the news is made.”

In this Boy’s Own world he can smile at the doctors’ enthusiasm for travelling by helicopter to bring back casualties.

“Given that working as a doctor on the helicopter is both useless and very dangerous, you might think that we would be having difficulty staffing the air ambulance. Not a bit of it. Everyone, myself included, fell over themselves to have a chance to fly as a doctor.”

Relationships between doctors, he noted, developed quickly in Afghanistan.

“It is perfectly possible back in England to work for years alongside a colleague and never know that they are a top amateur opera singer in their spare time. But over there, the long periods of quiet between each storm of activity is a licence to probe.”

He learnt the thing they all seemed to share was a hunger for calculated risk taking.

He noted that many of his colleagues owned large motorcycles, others being into diving and parachuting.

The work certainly satisfied his craving to do something new, when between treating gunshot wounds and burns, he came across certain conditions for the first time.

Even Prof Bulstrode was unsettled when a soldier arrived screaming that something was eating into his eyeball. He discovered it was larvae from sheep bott fly, which throws its young into the nostrils or eyes of sheep. It involved him in painstakingly removing the venomous larvae with a needle to save the soldier’s sight.

After three months, as he was preparing to fly home, he was invited to extend his tour by six months until April, only this time much of the work was focused on improving public health for local people, working for the Government’s aid department, the Department for International Development.

The job included visiting remote villages to hand out thousands of mosquito nets, which stop people contracting malaria and Leishmaniasis, a cruel insect-borne disease that proves particularly disastrous for girls, because the scarring makes them unmarriageable. The nets have insecticide in their fibres and have been shown to cut child mortality by 45 per cent.

For some of the time he served as a medical adviser at Bost Hospital in Lashkar Gah in Helmand. But he accepts the impact he could make was limited by a culture which allows men to open their bowels in streets where children play. “We suggested that we could build latrines, but no one wanted latrines because they’re viewed as dirty and smelly.”

As he prepared this week to fly out to India his week, where he will be examining young surgeons, Prof Bulstrode had no doubt the Afghanistan experience had changed him.

His staff and colleagues at the John Radcliffe see it, too, when they rush into his office with their problems.

“Crisis?” he will say. “This really isn’t a crisis at all.”