At 3,500 metres above sea level, altitude sickness kicks in quickly. In the arrivals hall, gasping tourists stagger towards the baggage carousel. My head starts aching as the hotel driver carries my luggage to his car. I ask him to carry me as well.

Leh is the capital of Ladakh, a region of Jammu and Kashmir, India's northernmost state. Known as Little Tibet, Ladakh is about the size of England with a similar population to that of Wan Chai. The name Ladakh derives from 'La Dags', or 'land of mountain passes', and is characterised by high-altitude desert surrounded by snowcapped peaks soaring above 6,000 metres.

Leh is a popular base for trekkers and is one of the best places in which to study Tibetan culture. Evidence of the town's position at the crossroads of ancient trade routes can be seen in the weathered faces of its inhabitants. Kashmiri merchants rub shoulders with Ladakhi shepherds and Tibetan monks haggle with Punjabi businessmen.

Newer arrivals laze in cafes drinking masala tea and waiting for the symptoms of altitude sickness to subside. Compared with Hong Kong, the air seems incredibly dry - you're more likely to encounter a yeti than a dehumidifier in these parts.

Leh is also the starting (or finishing) point of one of the world's great road journeys. The 475-kilometre drive to Manali, in neighbouring Himachal Pradesh, is spoken of in revered tones. Numerous websites sing its praises - and warn of treacherous conditions.

When I ask, travel agents say the road is still snowbound, although there are rumours it could open for light traffic within hours. I meet Kanchuk, who says, for a small commission, he can get me a place in the first southbound jeep of the season. It's a good deal. He does the bargaining while I go sightseeing.

The view from the 17th-century Tibetan palace overlooking Leh helps visitors orient themselves, with bird's-eye views of a dusty, medieval-looking settlement that sprawls along the Indus River Valley.

A leisurely day can be spent exploring nearby monasteries. Hemis is famed for a two-day festival held in mid-July; at Thiksey, a series of buildings cling to the edge of a craggy ridge; and monks show visitors around the austere cluster of temples at Chemrey. My guide has a mobile phone that matches his burgundy gown and plans to open a coffee shop in Leh so he can meet more foreigners.

Helena Norberg-Hodge has been visiting Ladakh since 1975. In Ancient Futures, the Swedish author describes what she sees as an identity crisis caused by the introduction of a market economy, which has led to job insecurity, competitive rather than communal living and an increase in crime.

Seduced by the trappings of the West, Ladakhi youths in particular have become embarrassed by their own 'backward' culture and are rushing to adopt foreign clothing, lifestyles and habits, notes Norberg-Hodge.

Kanchuk joins me at the German Bakery. Puffing on a Marlboro, he refuses to take off his Ray-Bans even though one of Leh's frequent power cuts leaves us in near darkness. The good news is he has found a vehicle heading to Manali. The bad news is it leaves at 2am, for reasons he neglects to explain.

Leh bus station is deserted except for seven shivering strangers tying luggage onto the roof of a jeep and squabbling over seating arrangements. I've paid extra to sit in the front, so I can bribe the driver to stop when I want to take photographs and also in case I need to poke him in the ribs if he nods off.

I'm travelling with two Muslims, two Hindus and two Buddhists. The journey will take at least 20 hours, which gives me plenty of time to come up with a joke.

We follow the beam from our solitary headlight until the rising sun paints the surrounding mountaintops scarlet. The early morning light also reveals how far down the valley floor is. The jeep wheezes over Taglang La, which, at 5,328 metres, is the second-highest motorable pass in the world.

There are few settlements en route but whenever we arrive at an army checkpoint I urge our driver, Amit, to drink some sickly sweet Indian tea for energy. On these hazardous roads, if he drops off, we all drop off.

Tibetan herders populate the high plains and yaks graze near the snowline as we lurch higher. Each vista is more jaw-dropping than the last. We pass turquoise lakes and rivers swollen with snowmelt. We ford streams and negotiate boulder-strewn river beds that turn out to be the highway.

After 18 bone-shuddering hours it's time for the final ascent. The notorious Rohtang Pass includes a precariously muddy single-lane ledge with overhanging cliffs on one side and a 3,000-metre precipice on the other.

Rohtang, or 'pile of corpses' in Tibetan, holds no fear for my fellow passengers as they're all fast asleep, heads lolling on each other's shoulders. Clouds engulf us and visibility drops to five metres. Amit chooses this moment to put his foot down.

We corkscrew downwards through a series of switchbacks. As the only passenger uncertain about the existence of an afterlife, I'm mightily relieved when we finally reach Manali - a former British hill station set in an idyllic valley of apricot and apple trees. The journey has left me numb with exhaustion, anxiety and frostbite. It has taken years off my life.

I might well do it again next year.