As the train pulled out of Beijing’s huge West Station to the strains of Auld Lang Syne, the excitement among the 800 or so passengers was palpable. We were at the start of a 48-hour journey that would inaugurate one of China’s great engineering feats — a railway to the Roof of the World.

First things first. Having installed my luggage on the bottom bunk in my six-person hard sleeper compartment, it was time to inspect the facilities. How were the loos? Shiny steel squat facilities, as in every other train in China. So nothing special then on the first train to Lhasa, capital of the Himalayan region of Tibet.

Since departure time was 9.30pm, the restaurant car was not serving food. But it didn’t take long to discover that, even at that late hour, beer was available for a price. Entertainment was limited to recorded announcements — in Mandarin and English — about the achievement that is the train, Tibet and its traditions and protection of the environment. I returned to my bunk and was soon tucked up between clean white sheets and nodded off to sleep. But sharing a tiny compartment, without a door, with five other people and the rattle of the breakfast trolley up and down the train to feed several hundred passengers made dozing beyond 7am impossible.

The food could not be described as the high point of the journey. Rice, pickles, a boiled egg and a preserved egg along with a chunk of sweetish bread and a box of sugary orange juice constituted breakfast.

Looking out at the scenery as the train trundled across the plains of central China soon palled. The towns that we flashed through offered a monotonous array of concrete blocks, chimney stacks and factory compounds.

Only lunch — another tray with rice, stir-fried vegetables, a couple of chicken wings and some pork in a brown sauce — enlivened the day. But anyone coming on this journey isn’t there for the food.

Before the Government found a couple of billion pounds and some very innovative engineers, the railway used to end, abruptly, on the outskirts of the town of Golmud in Qinghai province. Now, built over treacherous permafrost, the highest railroad on Earth snakes its way all the way to Lhasa. It’s a construction feat that few, even in China, believed could ever be achieved. It seems destined to become one of the world’s legendary train journeys.

Just before dawn, the express ground to a halt with a squeal of brakes in Golmud. Passengers scrambled into down jackets and disgorged on to the platform. The green engine typical of all other Chinese trains, which had pulled us almost 3,000km (1,750 miles) across China, was decoupled. Out of the gloom appeared three gleaming white locomotives, built in the United States and each of 3,800hp. Engineers have assessed that this is the only way to generate the power necessary to pull the 16 carriages up to the high Tibetan plateau where the thin air stretches the capacity of both man and locomotive.

Within minutes, Golmud and the plains had disappeared. The restaurant car with its picture windows offered the ideal place from which to view our progress.

Vast vistas opened up on both sides. Empty grassland was bordered by hills purple in the morning shadows. In the distance there were glimpses of snow-capped peaks. Then the train began to climb. The locomotives pulled their charges up the railway equivalent of hairpin bends. Looking back down the valley it was clear how rapidly we were gaining altitude when we could look down on bridges crossed just minutes earlier.

Smoking was forbidden after Golmud as oxygen began to pump through the carriages to help passengers to breathe as we climbed. Outside the window, trucks and cars dotted the road that for decades had been the only route from Golmud to Lhasa and now wound parallel to the train.

The wildlife was unexpected. Herd after herd of yaks. These burly, hairy beasts with fearsome horns broke away into a delicate prancing trot as the train clattered by. Elegant little gazelle grazed a mere stone’s throw from the line and as we gained height the numbers increased. A sighting of the endangered Tibetan antelope would have been a treat, but was not to be. However, rare wild asses galloped away in the distance as we neared the highest point of our journey: the Tangula Pass.

By this stage some passengers needed the additional oxygen outlets with which each seat is fitted. Some said they felt faint and queasy as they sat with oxygen tubes clipped to their nostrils. A hit of the oxygen seemed to help a little. But I found the altitude exhilarating rather than exhausting. I even found space for a little tray of lunch, delivered with a grin by the waiter who pointed to the ribs and said: “Yak. That’s all we can get here.”

The altitude made it impossible to boil water, so instead of rice for lunch, we had steamed bread rolls that had been loaded on to the train at Golmud.

And the American locomotives were so efficient that we reached Lhasa with an hour to spare. It’s a city where every extra hour is a joy. To trail the stream of pilgrims circling Tibet’s holy of holies, the Jokhang Temple, is to feel a depth of religious faith that has endured for centuries, surviving appalling persecution.

All trains are now travelling at full capacity, and China is urging its people, who could never before afford the air fare to Lhasa, to be patient and delay their trip until next year. With 3,000 tourists streaming off the trains each day, it seems Lhasa is best visited sooner rather than later — before the flood of Chinese travellers changes this Himalayan eyrie for ever.

Need to know

Getting there: GW Travel (0161-928 9410, www.gwtravel.co.uk) has a ten-day rail journey from Beijing to Lhasa, including the Roof of the World, leaving on September 21, 2007. From £2,995 (flights not included).

Great Rail Journeys (01904 521980, www.greatrail.com) is finalising a new 19-day escorted tour for early August 2007. In Search of Shangri-La will start in Shanghai and include the Roof of the World and a stay in Lhasa. From about £4,500, flights included.

Audley Travel (01869 276217, www.audleytravel.com) is planning a two-week group tour to Tibet, including a trip on the Lhasa Express next October. From about £2,500 (flights not included).

Useful website: www.chinatibettrain.com.

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