Ablond border guard wearing long braids waves us out of Russia - and the road immediately turns to dirt. Our van shudders through a barren no-man's-land deep in the rocky Altai Mountains, but on our arrival, we find that the gate to Mongolia is locked.

The country is closed for lunch.

Thirty-nine days and 14,500 kilometres after having left London as a participant in the Mongolia Charity Rally, our once shiny, finely-tuned van is covered in mud and sounding like the automotive equivalent of a 90-year-old smoker. There are still another 1,800 kilometres to go to our destination, the Mongolian capital, Ulan Bator, across some of the harshest and least-populated land in the world. I'm worried our van isn't going to make it - but first, someone needs to unlock the gate.

The remote Tashanta-Tsagaannuur border lies in the region where Russia, Kazakhstan, China and Mongolia converge. The highway on the Russian side of the border rises steadily to this point, the pine trees and wooden farmhouses of Siberia giving way to the golden grassland of the mountain steppe. It's Mongolia's only western border with Russia, and cars are lining up behind us.

At 2pm, the gates open. Importing a car into Mongolia takes a lot of paperwork. I've heard it can take five days, so we stocked up on vodka in the only store in Tashanta. But just after 6pm, a border guard beckons us over and accepts US$10. We're in.

The far western Bayan-Olgii province is majestic, high and cold, the vast steppe stretching to glacier-topped mountains that rise like jagged shark teeth. Skittish goats and shaggy baby yaks wobble past. Men and women in traditional deel, worn like thick bathrobes, bounce by on motorbikes. Massive golden eagles, their wingspan up to 2½ metres, perch like sentinels, some on rocks, some on the road and others - those owned by people - chained to posts or tyres. As Genghis Khan did before them, the eagle hunters of Mongolia train their birds to hunt wolves.

We pull over and make camp on the steppe. There are no fences; the land is owned by the state and used by the nomads. Their small horses and white gers (tents) dot the horizon. The sweeping expanse and the tiny funnels of smoke drifting from the tents' domes are disorienting; it feels as though there are more than 360 degrees here.

As dusk falls, other travellers join our camp; some Mongolians roar over on motorbikes, the vodka comes out and suddenly it's a party. The Mongolians challenge us to an impromptu wrestling match - the first to touch the ground loses. Of course, the locals win; wrestling has been a national sport here for 2,000 years. Eventually, the Mongolians roar off across the dark steppe, back to warm, felt-lined gers.

It's August and night temperatures drop to about nine degrees Celsius. In winter, though, they regularly fall to minus-30. And then there are the dzuds, winter storms so brutal they each decimate millions of head of livestock and leave entire families destitute. The nomads, who have lived here for thousands of years, are supernaturally tough.

The next morning we head into the provincial capital, Olgii. Low-rise brick buildings and ramshackle concrete structures line dirt roads filled with motorbikes, old Russian 4x4s and plastic bottles. Two boys in shower slippers walk a calf down the middle of the road.

Having a small airport, Olgii sees a trickle of tourists, mostly in summer and during October's Golden Eagle Festival. Many head for glacier valleys high in the Altai Tavan Bogd National Park, where thousands of prehistoric petroglyphs depict 12,000 years of hunting and herding, and include representations of mammoths, rhinoceros and ostriches. The park is only 180 kilometres from Olgii, but that's a full day's drive.

The roads are tough. Sand becomes dirt becomes mud becomes rock. Multiple tracks all go in roughly the same direction. We use the compass and look for tiny dust clouds on the horizon: evidence of a road. Often, a track goes straight into a river.

Nevertheless, there is immense freedom driving on your own out here among all this wild beauty.

Unfortunately, our van is sounding worse by the minute. A few hours outside of Olgii, we bottom out hard and the van gives up altogether.

We are given a tow by another rally team into the little Kazakh settlement of Tolbo. It's a high and lonely place, near the large Tolbo Lake, with a single dirt road running past the only store, a few houses and a blue-domed mosque. I pay a woman named Janis, who runs the store, to park my van in her backyard until a mechanic from Ulan Bator can come and rescue it (the van will be donated to the charity Go Help once it has been taken back to the capital). It will be safe here from the drunks, she says. Almost on cue, a man lurches past, moaning.

"Drunk," Janis says, looking at me knowingly.

We hitch a ride out with the other rally team. The night is cold and clear. I've never seen so many stars. One shot across the black sky while we were in Janis' backyard. Mongolians say it's not good to see a shooting star; it means someone is dying. I, however, couldn't have felt more fortunate.

It takes six more days to cross Mongolia. We camp in places so stunningly beautiful they seem unreal, get lost (apparently, there are four towns named Altay), nibble on hard cheese made from dried sour milk, pay a dollar to hold a huge golden eagle and play card games by flashlight in a muttony ger.

Driving into Ulan Bator is anticlimactic. On the fringes sprawl the ger districts, low-income areas in which most of the city's population live. In the centre, the money pouring in from the mining boom is obvious. Expensive cars plug streets lined with Irish pubs, European bakeries and pizza joints. There is even a North Korean restaurant. A 70-million-year-old dinosaur skeleton stands in the main square, next to a statue of Genghis Khan. Ulan Bator is an odd but intriguing city.

On my last night, I go out for Mongolian dumplings and farewell margaritas. If someone were to give me a car to drive back, I would gladly do it all again. I would, though, take Mongolia at a much slower pace.

The next day, 51 days after leaving London, I fly to Hong Kong. It takes less than five hours to get home. Driving is a lot more fun.