Afghanistan is still one of the world's most dangerous places — the wounding of nine British soldiers in a “friendly fire” incident is a bitter reminder of that. But the hidden menace in these summer months is the heat. With temperatures climbing beyond 50C the force of a relentless and unforgiving sun in the high altitudes of northern Helmand can be, as I discovered in traumatic circumstances, a potential killer.

I was one of a group of four journalists visiting one of the farthest outposts of British-held territory at Musa Qala. We had flown out to the forward operating base known as FOB Edinburgh, about four miles to the northwest, where coalition forces defend the town from encroaching Taleban fighters. A few days there, watching soldiers of two Scottish battalions (Argylls and Highlanders) mount patrols in their Warrior and Mastiff vehicles, suggested that these tanned, muscular and unfailingly cheerful young men had acclimatised well to the searing heat. They had even set up a gym outside in the dust, where, stripped to the waist, they pumped iron in the midday sun.

“We came out in March, when the heat's not so bad,” said one officer, “but we still think it takes seven or eight weeks for the Jocks to acclimatise.”

When they go out on patrol, they may be carrying ammunition and supplies as heavy as their own body weight, so their resilience in the sun is remarkable.

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Fitness is not, in itself, a defence against heat, and some soldiers find it harder to adjust than others — the hospital at Camp Bastion has dealt with far more victims of heat exhaustion than of roadside bombs. For journalists like us, however, neither fit nor acclimatised, the experience was of living, day in and day out, in the searing heat of an open furnace.

It was when I got to the camp at District Centre, Musa Qala, where the Scots and the Afghan National Army share quarters, that I began to succumb. Despite drinking litre after litre of water, as recommended, a dreadful lethargy, the draining of all energy, and a paralysing listlessness overcame me. I could do nothing, except lie immobile on my camp bed. It was noticed immediately by Captain Stevie Rae, who was in charge of our group, and he took me to the medical centre — a tent with basic medical supplies and a fridge that had arrived only a few weeks ago.

I was checked by the medical team headed by Captain D Cooper, who found that my body temperature had climbed from a normal 37C to a potentially lethal 38.5. I was laid out on a stretcher, put on a saline drip, given strategically placed ice packs (under the arms and between the legs) and sprayed with iced water to bring my temperature down. Within an hour I felt fine. Next day, however, despite staying in the shade, I had a relapse. This time my temperature was over 39C and Captain Cooper was worried that it was not responding to treatment. He kept me in, put me on another drip and ordered one of his team to fan me with a sheet of cardboard — a latter-day punka wallah whose services I greatly appreciated.

Meanwhile, however, a far greater drama was taking place. A female colleague, out on patrol with the US Marines and the Afghan National Police, in full body armour and helmet, with the temperature calculated at 54C, had gone suddenly sheet-white, started trembling violently, and then collapsed. Worried Marines put her into a Humvee armoured vehicle and began the hazardous drive back to camp. The road ahead was being routinely checked for IEDs (roadside bombs), but as her condition deteriorated, the order was given to bypass the checks and head straight for the camp gates — saving a life took precedence over security.

I was still in the medical tent when she came in. Immediately a full-scale team assembled, her clothes were cut off, a drip inserted and crucial treatment began. A senior officer summoned a Medical Emergency and Recovery Team (Mert) from Camp Bastion, half an hour's flight away by Chinook helicopter, and told me to be on it too. As my colleague's condition deteriorated, there was a palpable sense of crisis inside the suddenly crowded tent. Within half an hour, her body temperature had soared to 43C — a life-threatening level. I got dressed quickly and was ordered out to the landing strip. “I think you know that her condition is very grave,” the colonel in charge informed me.

A medical evacuation (“medivac”) from a war zone is an operation of high drama, but a meticulously practised routine. Chinooks do not normally come into Musa Qala, so armed soldiers guarded the area and purple smoke was put up to guide the machine in.

By now the patient had arrived in a military ambulance, under protective foil, and guarded by soldiers.

As the helicopter clattered in at maximum speed, the dust came up in an impenetrable cloud. A soldier took me by the hand and hauled me, stumbling over the rubble of the landing area, and through the blasting heat of the Chinook's engines. The rear ramp came down and the stretcher went in immediately. I followed with our kit, and sat, within a foot of the stretcher. The patient was unconscious. A burly Irish sergeant squeezed my knee reassuringly. “She'll be fine,” he said. I wasn't so sure.

The Mert was made up of Lieutenant-Colonel Duncan Parkhouse, of the Royal Army Medical Corps, Flight Sergeant Mark White, a paramedic, and Corporal Margaret Carthy. Wearing helmets and body armour, they are trained to work in conditions as far removed from a hospital operating theatre as it is possible to imagine. The Chinook travels within 50ft of the ground, wheeling to avoid potential rocket attacks. The noise inside is deafening, the light dim, and dust swirls everywhere. Nevertheless, over the next half hour, the team had to insert a syringe into an almost non-existent vein, clear the patient's throat of vomit and set up a drip.

All I could see was the patient, the two medics and the colonel's face as, squatting by her head, he battled to save her life. I shall never forget that scene: his head bent over his patient, his face creased with concern. And then, as the Chinook raced across the desert, her heart stopped. I saw, feet away, a drama as intense as any I have witnessed. Colonel Parkhouse threw his body armour and helmet off, spoke orders through his mike, began the resuscitation process. Sergeant White thumped her chest, another soldier was summoned to squeeze an emptying sachet of fluids. The team worked urgently together.

The only evidence I had as to whether they were winning or losing came from Colonel Parkhouse's face. Three minutes went by as we all held our breath — and then he smiled. The corner had been turned. The sergeant held up five fingers — five minutes to Bastion. We willed the Chinook on.

As we touched down, an ambulance was waiting, and within minutes the patient was in intensive care. An hour later, as I lay recovering from my minor relapse, word came out that she was fine. Not only had her life been saved by the professionalism of the Chinook medical team, she was making a full recovery. We had, however, learnt a stiff lesson about severe heat and what it can do to the human body.

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