My race started on the fourth day. We’d already run 70 miles over three stages - through the stifling heat of the Gobi Desert; scrambling down and up countless dry riverbeds worn into the parched, desolate landscape. Now we were in the foothills of the mighty Altai mountain range: a barely touched mosaic of alpine meadows, spruce forests and glaciated peaks along the border between Kazakhstan and the far northwest of China.

We rose with the sun and the now-familiar ritual began. We stretched our tired legs and delicately protected blisters and sore spots with plasters and tape; we climbed back into the same old pungent running clothes and rehydrated pouches of porridge as we listened to the pre-race briefing; we repacked rucksacks with what remained of our supplies for the week, made a dash to the delightful al fresco bathroom facilities and headed to the red banner marking that day’s start line. Sam from 4 Deserts counted down to the 8am start and we were off again: 100 runners and walkers fully aware of the 40 miles and 900m of ascent between us and our next dehydrated dinner.

A backmarker keen to get photographed in first place attacked, then faded, and we each settled into our own rhythm – mine set by the iPod Shuffle I had brought loaded with a single track: a 180bpm metronome. Double Olympian “Chema” Martinez shot off into the distance, pursued by Sebastiano Arlotta-Tarino, and I found I had acquired a second shadow. My new closest friend was matching me pace for pace: if I slowed, he slowed; if I leaned into a faster run, he did too. The runner in second position overall, TNF-sponsored former para Sam McGrath, had been forced out with a knee injury on day three and I was elevated into a podium position. I was now a marked man.

We rolled over a few miles of undulating scrubland to the foot of the mountains - dodging innocuous-looking bushes whose spines – almost invisible to the eye – were leg-laceratingly sharp; our nostrils hit by occasional wafts of wild thyme. The previous day we had been pelted by sleet and hail before knee-deep snow on the final pass forced race organisers to cut the stage short, but now the air was still and the sun hung high in a crystal-clear sky, while me and my shadow got stuck in to a steep off-trail climb to a path some 500 metres above.

As we ran along the ridge line, enjoying the breeze and stealing glances at the pure white peaks across the valley, we were greeted by rousing shouts of “jia you, jia you” (“go on, go on”) from the security guards dotted along the Kazakh border. Whole families turned out to watch us pass and shepherd boys on ageing Japanese motorbikes followed us along the trails, taking photos of our strange procession on their mobiles as they rode.

The glorious high pastures seemed to stretch for ever. This is what I was here for, I thought, as I enjoyed one of my best ever days of mountain running. This is why I left my family and friends for three weeks and overcame my fear of flying to travel to a remote province that few have heard of; to carry a week’s food and clothing on my back and struggle for sleep in a tent pitched on uneven, rocky ground.

A few hours and a few hundred more metres of ascent later, we hit a stony jeep track and followed it back down into a valley as it turned to tarmac. My shadow attacked: upping the pace to around six minutes a mile as he tried to make up the time I had gained on him during cooler conditions on day two. I clung on for dear life, desperate not to let him know I was suffering. Thankfully he relented when he heard my breath on his shoulder once more and we settled into a friendlier pace – chatting occasionally – bemoaning the high sun and long straight roads lined with cypress trees but devoid of shade, which reminded me of hot summers in Italy.

The finish couldn’t come soon enough and we crossed together before collapsing in the shade and downing a few bottles of cool water – conscious that we had even further to run the next day.

Being back in camp early gave me plenty of time to recover, though. I tried to stick to a routine: drink a protein shake; lie with my feet raised for an hour; then blow up my mattress and rest again before the camp started getting busier. I’d borrow a walking pole to use as a massage stick and get to work on my legs, loosening the muscles and flushing out toxins. Then it would be time for a dehydrated meal for dinner, a chat round the campfire, and another session with the stick. Most people would head to bed as soon as it got dark. Luxury! I found I had far more time for rest and recovery in the Gobi Desert than I usually do in London – and consequently far fewer aches and pains.

The next day was the “long march”: 45 miles of farm tracks and mountains, with 2,440 metres of ascent. I’ve run a few ultras now so know the importance of pacing myself and have a good idea of the kind of speed I can maintain for nine or 10 hours. The previous day’s competition with Andrzej had shown us both that, while we were fighting each other for that podium place, we were also well matched for pace and had similar tactics for travelling fast in the mountains: run all the downhills, flats and gentle rises and power walk the steeper sections. Just before the start we agreed to work together to create a gap on those behind and make sure we were racing for third and fourth, not sixth and seventh, before duking it out at the end of the day. That suited me just fine.

We were now in the foothills of the Tian Shan mountain range: following an easy jeep track through summer pastures. A teenage shepherd boy on a motorbike passed us five or six times as we toiled in the heat to reach the first pass 1,000m above. With his leather jacket, jeans and shades, multicoloured tassles hanging from end of his handlebars and dance beats blaring from his mobile phone, he looked to me like some kind of Mongolian easy rider: maybe not destined to spend the rest of his life farming in the mountains.

As the trail petered out and we struck out across country, the signs of human life grew faint, then disappeared. Marmots squeaked and hid as we ran through countless deserted alpine valleys; we saw herds of wild horses on the slopes above and mountain goats clinging to impossibly steep terrain. Still we matched each other pace for pace.

Suddenly I looked up and saw the flags of the checkpoint marking the final pass of the day. I reached into my pocket and fished out my last gel: a GU Espresso Love I had been saving all week. I forced down the thick, sickly sweet concoction, glugged the rest of my water and waited for the double caffeine shot to take effect ...

As we reached the checkpoint we were treated to a fine view down to the final camp on the shore of the deep-blue waters of Sayram Lake hundreds of metres below, a favourite haunt of Mongol ruler Genghis Khan. I passed on the usual water top-up and pushed straight on through. After more than eight hours pacing myself sensibly, always keeping something in reserve, I gave it everything in the final 5km flight to the finish. Leaning forward to stay perpendicular to the slope, hitting the track mid-foot and trusting my luck on stray rocks, I really cut loose for the first time all week.

I crossed the line and collapsed (again). Chema had finished 75 minutes ago and was already relaxing back in camp, but as I lay staring at the sky it felt fantastic to know I had run the best race I could on the day. Plus, I had stolen second on the stage and taken another 45 seconds out of Andrzej, increasing the gap to six minutes. That must be enough, right?

The first six or seven runners made it to the end of the long day in daylight – but for the rest out on the course it was time to strap on headtorches. My tentmates arrived one by one during the night. It was a weird feeling going to bed knowing some of them were still out there – although we were organised enough to leave them a handy stock of fresh water and some space on the floor. Day six was a rest day for most – although when a cheer went up shortly after 10am, it signalled the final competitors rolling into camp after 24 long hours out on the trail.

We woke on the seventh day with just nine miles round the lake between us and the finish line. I’d heard that in the last 4 Deserts run, the Sahara Race, the final stage wasn’t timed and many competitors jogged in together. To be honest I was hoping Andrzej would do the same, but while we were hanging around camp waiting for the off he grabbed a friend with better English to translate between us, and warned me that he wouldn’t feel right if he didn’t have a crack. Oh well, I wished him luck and gave him my most confident smile.

A multi-day race is a war of attrition: a managed decline. At the Gobi March I thought I had managed to stay on the right side of that fine line and I actually felt better by the long day than I had at start: my body adapting to the task at hand, learning to expect what I was going to put it through every day.

That was until Sam gave us the final countdown and Chema shot off round the shore; Andrzej hard on his heels. I had been feeling great: bouncing up and down on the start line, playing the mental game, knowing that we were pretty much the only two runners really racing that day. But it only took a few minutes to realise I had nothing left.

My legs turned to jelly on the shingle beach and I was quickly sweating and out of breath. I tried all the tricks which had served me so well all week – trying to keep a high cadence and leaning forward to let gravity take hold – but it just wouldn’t happen for me. I reached for the half energy bar in my pocket – the final piece of food from my seven-day supply – but I couldn’t even get the first mouthful down. I felt sick as I watched Andrzej disappear over the horizon. I was agonisingly close to the finish but the fear of failure quickly swept away my confidence and I almost started to think I didn’t care.

Of course, running isn’t about where you place and everyone was there to run their own race. For me, it’s about battling yourself, pushing to do the best you can. In the Gobi desert I was enjoying competing for a podium position; playing at being at the sharp end of an ultramarathon. But I’ll be chuffed with a top 200 finish in the UTMB this August or to come in the top 1,000 of the 2015 London Marathon – so I knew I was chasing an arbitrary target. I was still feeling pretty sore about dropping out of the Spine Race, though, and I’d been in similar situations to this before and come off worse: racing with someone all day just to lose out in the final reckoning. It couldn’t be happening again, could it?

In the end, six minutes was too much for Andrzej to make up. I knew I was in desperate need of an energy boost, so slowed to a walk to drink the rest of my water and get that half energy bar down. Then I turned on my metronome and steadily worked my way up into a brisk(ish) jog, hitting that magic 180 steps per minute and getting as close as I could to good posture after seven days running with a full pack. I did just enough. After 30 hours of racing over six days we were separated by a paltry three minutes. (Seba had an hour on us, with Chema a further three ahead of him.) I collapsed over the line (again!) to banish the spectre of my Spine failure and earn a weighty perspex trophy, which was nice.

On the buses back to the race hotel in Bole – caked in dust and salt deposits from seven days of sweat – it seemed like much longer than a week ago that we had started our journey.

Peter Mackenzie, a co-founder of Mainstream Publishing, was one of those who finished the long day in a little over 24 hours. He was taking part in the toughest physical challenge he’d ever faced with his son Nick and Nick’s partner Yevgeniya – an experience he described as “gruelling” but which left him with no regrets.

“It’s like one big family,” he told me after the race. “You get so much support – from other competitors, from the crew, the medics, the volunteers – I’ve never experienced that before and it just gives you spirit. That’s really what got us through. You go through pain but you get to the end, and that lasts: it makes it all worthwhile. I feel like we’ve really accomplished something.”

After my first shower in a week, a cold beer and a change into fresh clothes – running gear sealed in an air-tight bag – I felt human enough to reflect on the experience.

Watching fellow competitors stagger around camp like zombies in the mornings – tired, sore and nursing crocked knees, blistered feet or chafing in unmentionable places – was comic at times. It seemed mystifying that these privileged people had actually handed over money to leave behind their jobs, homes and families and put themselves through a week of pain and suffering.

As so often, running guru George Sheehan has the answer. He argued that we are wrong to equate comfort and convenience – the total absence of pain and struggle – with happiness. “We’ve grown so comfortable we’re miserable,” he wrote. After that race I’ve got no doubt he’s right: I feel like I found an antidote to modern life.