On the walk in to Sulamar, the odd carefully constructed section of trail had hinted that the route had once seen much heavier use than it does today. A bit of research had revealed that the trail dates back to the Tang Dynasty (c. AD 700) and had gone through various ups and downs over the years. It runs for about 150 kilometres from Xiate in the north to Aksu in the south, compared to about 2,000 kilometres by the lowland route. With these distances in mind it is perhaps unsurprising that many were prepared to risk the dangers of the higher path and the trail was an important trade route connecting the two centres of population. But the challenges of keeping it open were very real, and in its heyday up to seventy families lived at the side of the glacier section and were employed to maintain the trail. In the mid-twentieth century, the building of motorable roads on the lowland route signalled a decline in the usage of the high trail and, from what I have read, it was last used regularly in the 1940s when the Uyghur armies used it to launch surprise attacks on Chinese troops based at Aksu.

In the 1980s the significance of this historic trail was increasingly appreciated and in 1989 a Japanese team was reported as the first to travel the route in modern times. The second team to make it all the way was reported to be a Chinese team in 2001, although the leader of their party was swept away while trying to cross the fierce river emanating from the snout of the Muzart Glacier. Since that time it has been reported that ‘many had tried but few made it through’. This fearsome reputation had been reinforced by news we received at the beginning of the trip that three trekkers had been drowned on the trail just before our arrival. Curiously though, Abdhul reported that two trekkers had passed through base camp while we were climbing, having come all the way from the Aksu side and successfully waded the Muzart River in the early morning when the upper slopes were frozen and the water level relatively low. Intrigued, we were keen to explore the southern section of the trail, not only because it sounded interesting, but because it would provide access to the Chulebos peaks, an area of unclimbed 6,000-metre summits stretching towards the Kazakhstan border.

From our base camp there was clear evidence of the trail descending towards the chaotic rubble covering the glacier. Having no idea where the trail went next, we followed discontinuous streaks of bare ice down the centre of the glacier until, at the head of an icefall section, the terrain became so broken that awkward climbing and balancing along knife-edges of ice separating open crevasses was necessary. Even bearing in mind the changing conditions caused by global warming, this just didn’t seem right. We sat down and peered around. Progress in any direction looked difficult.

Although it had been gloriously sunny when we left base camp, mist filled the valleys. We had assumed this would burn off as the day progressed but by now it was nearly lunchtime and down by the snout of the glacier it was a grey and murky day with visibility of only a hundred metres or so.

Paul was in a positive mood.

‘I reckon it’s up there,’ he announced, pointing to the top of a horrific-looking moraine.

He was right. Over the years the moraine had collapsed in several areas but it transpired that over most of its length a delightful grassy ablation valley housed a still-recognisable track. At one point we even came across what appeared to be old horse or mule droppings, although with access difficult from both ends quite how such animals got there was a mystery.

At the Aksu end of the ablation valley high above a major icefall in the Muzart Glacier stood the readily identifiable remains of an old toll booth with thick walls and completely blocking the way. Nearby were the remains of what appeared to be the accommodation used by those charged with keeping the route open. The only way to have avoided tolls looked to be by braving the icefall we had experienced earlier. That seemed out of the question, so I can but assume that those in control had a pretty free hand in what they charged.

A steep track zigzagged up from the lower end of the icefall. Huge smooth walls of rock hemmed in the broken ice and it was impossible to gain the track from the Aksu side without climbing a few hundred metres of icefall. We had one axe between us, which was just about adequate. It was difficult to imagine this section being very different when the trail was in regular use and I didn’t envy those once charged with keeping the trail open to traffic.

The Muzart River flowing from the snout of the glacier was an angry mass of boiling grey water which appeared impossible to cross. Fortunately, we didn’t need to worry, as we were on the north side and the Chulebos valley that we wanted to explore was not far downstream on the same side.

Our permit only covered us for access to the north side of the range, so it felt slightly naughty to be beyond the end of the glacier on the south side. The odd piece of rubbish and, surprisingly, gas cylinders suggested visitors to this area, presumably from the plains to the south. It was just as I started to feel the need to be wary that Paul stopped ahead of me and stared quizzically at the ground.

‘Take a look at this.’

He pointed at an indistinct track in the sandy deposits between the rocks.

‘Tyre tracks.’

There was no doubt about it. A vehicle with huge tyres had been this way. We stared in disbelief, thinking of the force of the Muzart River, the crossings that were apparently necessary downstream and the drownings we knew had occurred.

‘Must have been an outrageous vehicle.’

There was no sign of any reason for such a vehicle to have come this way and we could only conclude that it might have been an army truck driver who had been bored and experimented with how far he could drive towards the glacier. Nevertheless, with the permit situation in mind we didn’t want to risk any awkward encounters and proceeded cautiously, wondering what other surprises might lay in store.

We did not have long to wait. Perhaps ten minutes later a huge square shape loomed out of the mist. I grabbed Paul’s arm and gesticulated wildly. We could hear no sound above the roar of the Muzart River. What could it be? There was no way to avoid it if we were to carry out our explorations as planned.

As we ventured forward cautiously the mists parted to reveal an ancient stone fort overlooking the plain at the junction of the Chulebos and Muzart valleys. It was perfectly positioned to guard access to the trail and was the ultimate symbol of the historic significance of this route. Although long-abandoned, the stature of the structure was clear and it didn’t take a lot of imagination to appreciate that the size and two-metre-thick walls would have made for an intimidating and impregnable fortress.

Now though, the place was derelict and quiet. With the mist clearing at last we could see that there were no other signs of human habitation in the area. What we could see was the churning, coal-black mass of the Chulebos River joining up with the Muzart River to flow on south down the Muzart gorge. How any vehicle had managed to cross such a forceful body of water prompted a lot of discussion between us. There was no doubt about it: it must have been a very large and impressive vehicle. And, we noted simultaneously, if we could somehow gain use of one in the future it could provide easy access to the mountaineering potential from the south.

Turning easily up the broad start to the Chulebos valley we felt reasonably certain that no Westerners or mountaineers had ever been this way before. It was an exhilarating feeling knowing that a whole massif of untouched 6,000-metre peaks lay ahead and we would most likely be the first to view them from close quarters.

Camping on a flat patch of alluvial sand we refreshed ourselves by swimming in a small lake of ice-cold meltwater and soaked in the spectacular view of untouched mountains to the south. Above us the first of the Chulebos peaks could be seen up a side valley. No stunning lines were visible, but we looked forward expectantly to what sights the following day would bring.

It brought a seemingly never-ending slog up the moraine covering the Chulebos Glacier. The broken surface and unstable rocks made for slow going. As the hours passed it became increasingly clear that the glacier was huge – a good thirty kilometres long – and time constraints meant that we would only be able to cover the first third. It was also becoming clear that as much as the Chulebos peaks make up a long ridge over 6,000 metres, the north side that we could see was snowy and did not appear to offer any eye-catching lines. Recognising that our tortuous progress was unlikely to open any new doors we ended by climbing up in to a delightful ablation valley behind a huge side moraine on the north side to soak up a final panoramic view before starting the trek back. If the Chulebos peaks had not particularly inspired us, the whole business of exploring definitely had.

We arrived back at base camp just after the horses had arrived and sat drinking tea as the animals were loaded. I pondered silently before breaking the silence.

‘I could get into this exploring business when I’m too old for mountaineering.’

Paul looked at me warily.

‘How long away is that then?’

I thought of the future. Objectives beckoned in east Tibet (lots), India, Bhutan, Pakistan … and then Pat Littlejohn and Steve Sustad were always hinting that I should join them on rock climbing trips to Ethiopia. I felt that perhaps I was back where I had started. There just seemed to be more objectives than time available.

‘Not yet,’ I heard myself saying.