The footprints in the snow were large, bigger than a human’s, with clearly defined toes. There was no sign of claw-marks. These prints looked as though they had been made only minutes before we arrived. I shivered and glanced around the deserted valley. We were the first Westerners ever to see this place, and we really hadn’t meant to come here.

Our expedition was in trouble. We had been trying to reach Gangkar Punsum, the world’s highest unclimbed mountain. This lies on the Tibetan border in Bhutan, the Himalayan kingdom to the east of Kathmandu which is rarely visited by Westerners.

The weather had been the worst in living memory, with rain or snow on every single day since leaving Thimpu, the capital. On day three, our packhorses were attacked by wild bees, and then our leader had suffered a back injury and was now lying in a crude shelter in the jungle four days behind, tended by our doctor. Our problem was that the high pass we had just crossed was now closed to our yaks by heavy snow. We couldn’t retreat that way, and the passes towards the mountain were closed too. We were trapped, and the 25 yaks only carried supplies for three weeks.

We had to get out before winter set in. As the five remaining Westerners, we could have attempted to re-cross the pass, leaving the yaks behind, but as acting leader I was unhappy about splitting the party even further. We had to stay with our tents and food. We also had a whole yak-herder family with us, including a young mother nursing an 8-month-old baby, so it was clear that we had to sink or swim together.

I asked our yak-herder Namgay Tsering for advice, and it was then that he told me of a lost valley that might provide a route back to civilisation, with two higher but easier passes that the yaks could just about manage in the snowy conditions. So the next morning we set off, guided by Pem Dem, the 20-year-old mother, with her baby Thinley. The yaks were being gathered up and loaded and would follow up behind us.

After a few hours, we walked up into the Lost Valley and Pem Dem sat down in the swirling snow to breastfeed her baby. It was only then that I noticed the solitary yak standing in the snow a few yards away. It seemed distressed. These animals are sometimes abandoned by the yak-herders when they are too old to carry heavy loads. This poor creature bellowed when it scented our baggage yaks coming up the valley behind. The significance of this animal was soon to be revealed.

 After feeding her baby, Pem Dem slung him onto her back again and we set off towards the Wangchum La pass at the head of the valley. We were all anxious about tackling this: at 16,400 feet it was the highest we had climbed so far, some 650 feet higher than Mont Blanc. It had never before been seen or crossed by Westerners. A few minutes later, just as the first bunch of baggage yaks stampeded past us, I spotted Sonam, our deaf-mute kitchen boy, pointing at the snow to the left of our path.

There they were: two footprints, spaced quite far apart, larger than human size. The left one was very clear, and my flesh crawled as I saw how the toes had curled into the snow for grip. The prints were larger than my own size-ten feet. My mind raced. I had to record this evidence and establish its authenticity in around twenty minutes. Any longer and I would be endangering our party.

While I filmed the footprints and took a snow sample, Predrag Jovanovic, our resident particle physicist, scouted ahead and behind the prints, which crossed our path at right angles, away from the solitary yak. He reported that in one direction the baggage yaks had obliterated all traces, and in the other our own footprints had done the same.

Yeti footprint photo
Image Copyright Graham Hoyland / Predrag Jovanovic

Had we disturbed a stalking creature? Was some large predator lurking behind one of the huge boulders that were scattered around the Lost Valley? I stood up and uneasily gazed up at the large boulders on the snow-covered hillside above me. Was there something up there that I couldn’t see but the old yak could smell? I crouched down again and took scrapings of dirty snow within the footprints for DNA testing. I didn’t want to try to remove the whole footprint, as there was a chance that we might have to retreat from the pass. In that case we could camp, re-examine the print and scout around for further signs.

I knew that anyone hearing our story would assume these footprints had been faked, and this was foremost in my mind too, and so I hastened forwards to the rest of the party. Had they seen the prints? Had they seen anyone bending down? The answer was a flat no. Everyone was too intent on getting to the pass, and anyway I had everyone in view just in front of me. No one had even hesitated. We set off again. I was frustrated that I had no time to record the prints in more detail, but at least I was fairly sure that there was no fakery: Pem Dem was too busy with her baby and with route-finding, and I was watching everyone else closely for signs of fatigue. Sonam, although obviously an intelligent and helpful man, was impossible to question, being deaf and unable to speak.

In the event we crossed the Wangchum La, becoming the first Westerners to do so and leaving the Lost Valley behind us. We then camped below the Saga La, climbed it the next day and were eventually reunited with our leader who was now recovered. Later in the expedition, two of us stood on the summit of a previously unclimbed mountain and gazed over hundreds of square miles of country previously unseen by Western eyes. There was plenty of terrain here for the snow leopards whose tracks we saw regularly, so why not a larger predator? We saw blue sheep and musk deer, so there was surely enough prey.

So, what was the creature? Was it a bear? The absence of claw-marks suggested otherwise. Could it therefore be the mythical beast that is spoken of all along the Himalayas: the Abominable Snowman, or yeti? Is the yeti really living in the unexplored wilderness of North Bhutan?

I decided to find out what I could about the strange world of mythical beasts: the cryptids.

When I gazed at those yeti footprints in the Lost Valley, I felt a mixture of fear and bewilderment. It was only later that I felt a connection to those who had gone before.

For nearly a century, Western explorers had been coming back from the heights with reports of man-like beasts in the Himalayas. They began with stories of strange footprints, then told of the violent deaths of their pack animals, killed with one savage blow. Their Sherpas told them that yetis were seven feet tall, covered with brownish hair. Their feet faced backwards, which made them confusing to track. The males had a long fringe of hair over their eyes and the females had pendulous breasts which they slung over their shoulders when they ran.

Your only hope of escaping from a yeti was to quickly determine which sex it was and then run downhill if it was a male, who would be blinded by his fringe, or run uphill if it was a female, who would be impeded by her breasts. Sometimes lonely males would kidnap Sherpa women and keep them in their caves, breeding strange children.

I decided to look back through the years and try to disentangle myth from reality, cryptozoology from science. In thirty years of climbing in these mountains, why had I only seen footprints? Why had no one managed to capture one of these fabled beasts? Where did they live, and could I find any solid proof of the yeti? Furthermore, was there any evidence for Bigfoot, the yeti’s American cousin?

We humans have only identified about two million of the estimated 10 million living species on our planet, and new species have been discovered in modern times that scientists had previously refused to accept.

There was good reason to believe, therefore, that I had been close to a large primate unknown to science. Had I disturbed the beginning of a stalking manoeuvre which would have led to the violent death of the solitary yak? The predator would have to have been big enough to take on a yak bull, with jaws and teeth powerful enough to kill it. Or would it despatch the animal with one savage blow, and then turn towards me?

Read more about what happened on that fateful day in my book, Yeti: An Abominable History