The next day I woke up to a seven-year-old piping Amdo songs. Dickir Ziggy had shared my bed while Tsedup had stayed with his brother, Gondo, on the other side of Machu. We lay and chatted about my brother Phil and his naughty antics as a child while the frost gathered on our breath. She was especially interested to hear the story I told her about him lying in the road and pretending to be dead. When the cars had stopped to see what had happened and the drivers got out to check on him, he would jump up laughing and run away. Ziggy giggled.

I went and washed in the cold stream in the morning sunshine while the sheep collected curiously around me. In the tent I made tsampa and the milk boiled over in the pot on the fire, leaving a pungent smell from the burnt splashes on the clay. Outside, Gorbo led the white stallion across the open entrance. It was the most seductively beautiful creature I had ever seen; pure white and graceful, like a unicorn without the horn. The tents had all but disappeared now. The river valley looked bare, apart from we few stragglers, and the dung mountains that the early movers had left behind. Next door Annay Urgin's tent had gone and only a lonely clay stove was left on the ground where her home had been. The nomads never destroyed a fire. I had watched the tent being dismantled while everyone stood fussing round the yaks, packing huge sacks of belongings – cheese, butter, barley, clothes, the altar, tent poles and the tent itself – on to the animals' backs. Excitement and change had permeated our daily routine and I was looking forward to our move in a few days' time. We had been away in Labrang during the first migration and I was not going to miss this experience. But first we had to go visiting. Apparently this tribe was bigger than I had thought and we had been invited to the other half by the families on the opposite side of Amnye Kula. Tsedup promised we would be back in time.

I was collected by jeep from the town and driven to a northern valley on the other side of Machu by Namjher, a jovial, portly man. Tsedup followed behind on the bike. He had known Namjher since birth and had grown up with all of the people I was about to meet. It was a sad fact but today the tribe was split in half. During Tsedup's years away the introduction of new legislation from the government meant that there were now land-division policies, with which the nomads were forced to comply. Large tribes were discouraged from cohabiting in favour of small groups of families occupying their own sections of land within the wire-fenced boundaries. A way of life that had been practised for centuries had been changed irrevocably. The very nature of nomadic pastoralism was at threat.

Before the legislation, a meeting of the heads of the eighty tribes in the Lhardey Nyima area, north of the Yellow river, would have determined where and when they should move within their vast grasslands. Tsedup remembered the land available to his own tribe as covering an area of between ten and twenty miles. At that time, they also moved more frequently, every month in the summer, to allow the grass to regenerate more quickly. Today they were confined to moving only three times a year within their designated areas and the grass was of poorer quality.

When the nomads had been given the order to divide up, they had been left to sort it out for themselves since the authorities did not have the ability to organise vast areas of nomadic pasture and were concerned about tribal conflict. A group of officials inspected it annually to ensure that the nomads had conformed to the guidelines, and enforced restrictions if they thought there had been any cheating. The Tibetans also had local influence in the form of governors, such as Tsedup's father, so a method of democratic demarcation was employed, in the same way that they had always organised their choice of settlement. They divided it up with dice.

In Tsedup's tribe they had thrown three dice to see who had the choice of land, and the size of each tract was decided according to population numbers. Their land encompassed the stretch from the valley to the north of Kula down to the Yellow river. They decided to divide the tribe in half. A natural split emerged, with certain families wanting to stay together. From that day the two halves would live separately and see little of each other. The original tribe had consisted of fifty families, and today twenty lived on our land to the south of Kula and the remainder with Namjher in the north. I thought it a tragic rift.

Tsedo and some of the other men from our half of the tribe had wanted the northern land, as it was deemed more sheltered and had better grass at the time. Where we were, on the flat grassland, the wind could sweep mercilessly down the river valley whipping up the topsoil of the overgrazed land and further eroding it. However, when we arrived at Namjher's half of the tribe it was clear that they were not doing so well. The valley was steep and heavily grazed, covered in heather and sparse areas of grass, which had dried up in the winter sunshine. It was beautiful with the snow-capped Kula rising majestically above us, but because of its northern aspect, it was also shady beneath the mountain slopes and in these dark shadows the temperatures were at zero and below. Ironically, this place had turned out to be the worst of the two sites, although Namjher's half of the tribe had chosen it.

They had already all moved into their winter houses and their dwellings were at various stages of comfort. Most were clay-built, with wooden roofs and brick floors, sparsely decorated, with newspaper displacing wallpaper and the odd picture of a Chinese pop star. We were greeted with warmth and hospitality by our hosts, most of whom were relations. Tsedup explained patiently who was related to whom and by what connection, but it was so hard to keep up with that I was soon lost. We had come with Aka Choedak, a monk who was a relative and who had also been in India. He was a cheerful soul, always laughing and chatting. He accompanied us to each dwelling – where we must have been offered about five hundred momos in all, and at every house a plate of djomdi, small brown beans dug from the earth, with rice, sugar and melted butter. When we reached the last house that day, we were forced to decline any further sustenance and sat sipping bowls of tea.

I had the greatest pleasure in meeting one relative who was tirelessly inquisitive about life in the West, staring intently with the smallest, most close-set eyes I have ever seen, exclaiming, 'hschuck chair! Scary, wow!' over and over as he listened to Tsedup's descriptions of routine things, such as trains that carried people under the ground. Tsedup spoke with authority about life in England. He sounded confident and settled and yet I knew that, deep down, he was neither back home. He still felt like a stranger. England hadn't matched up to his expectations and he had found it hard to forge a living there, but now we were in Amdo, I was glad that he sounded proud to be part of that life in the West, for it had rarely appeared so when we were there. I supposed that the grass was always greener on the other side of the fence.

That night I went to bed earlier than the rest of the throng, who carried on into the small hours. I was slightly overcome by the heat from the iron stove in Medo's tiny house and bewildered by the language barrier. I found it hard sometimes to appear attentive at these gatherings, as after a while of not understanding a conversation, my mind would wander. I retired to Namjher's house, and slept wrapped up in my tsarer next to Aka Choedak, who was snuggled up in his fuchsia robes. I had never slept in such close proximity to a monk before, and although we were separated by a low table in the middle of the platform, it felt sacrilegious.