As the train climbed towards the highest railway pass on Earth, funny things began to happen.

Pens leaked. Air-tight bags of crisps and peanuts burst open. Laptops crashed and MP3 players stopped working. Passengers began feeling nauseous, and some reached for their oxygen masks. A few were sick.

But few of the 500 passengers on board were complaining. For railway buffs, this was as close as it came to paradise. We were on board the first passenger train to journey the 4,000km (2,500 miles) from Beijing to the ancient Tibetan capital of Lhasa and the final 1,110km yesterday took us up through the 5,072m (16,640ft) Tanggula Pass and across the roof of the world.

As the 19-car T27 train climbed around hairpin bends on banks and bridges, Ivor Warburton could hardly contain his excitement. “This is everything I had hoped and a bit more,” the former British Railways executive exclaimed.

Outside the sealed windows, protected by ultra-violet filters, shaggy yaks ran startled from the train, rare antelope grazed on the grasslands, snow-capped peaks glistened in the sun and fat marmots scampered into their burrows.

This journey was made possible by what President Hu of China called a “miracle” of engineering. “We have the courage, confidence and ability to stand among the advanced peoples of the world,” he declared when he officially opened the line on Saturday.

It took more than 30,000 workers five years and more than £2.3 billion to build. About 550km of it runs over unstable tundra, requiring raised causeways and underground cooling pipes to prevent the ice melting. It is the world’s highest railway, surpassing Peru’s Lima-Huancayo line, which reaches 4,800m, and the highest station is in Nagqu, a town at 4,500m (14,850 ft).

Chinese officials consider it a testament to the success of their country’s economic reform and its rise as a major world power. State-controlled newspapers published pictures of villagers waving at the pssing train, and television showed President Hu congratulating workers who built the line.

But the line is also a political statement. It cements Beijing’s writ over Tibet, 56 years after the Chinese army marched into the remote Himalayan fastness. Along the line, paramilitary People’s Armed Police were stationed at intervals of about a kilometre, each standing at attention, back to the train, gazing out over grasslands where scarcely a human being was to be seen.

“The People’s Armed Police are here to protect the railway” read a banner at one station, though they may be more worried about scavengers eager to steal the rails than saboteurs wanting to disrupt services.

Previously, the journey from Beijing to Lhasa would have taken days, if not weeks, by road and rail. It can now be completed in 48 hours, for a fare of as little as £25 for those prepared to sit bolt upright on hard-backed chairs.

The one-way air fare of more than £200 is beyond the reach of most Tibetans and Chinese, and hardly an adventure. The rail journey takes you from one of the most densely populated parts of the planet, through endless hours of farmland, and then up through the rocky desert of the Himalayan foothills into boundless grassland.

Yesterday the train left Golmud — once the last station on a line that used to end abruptly in the sands of Qinghai province — at dawn.

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