www.bbc.co.uk In Timbuktu, camel trains, that for millenia have been trudging around the Sahara with their valuable cargoes, are being replaced by the much less exotic lorry.

I have always been fascinated by the Sahara - so when I heard that camel caravans still make the 450-mile journey from the Taoudenni salt mines to Timbuktu, I decided to go and see if this was true.

What I found there was the stuff of dreams. Every week between November and February, caravans of up to 50 camels set out from Timbuktu on the month-long round trip.

Each camel brings back four huge slabs of salt, the so-called "white gold" of the Sahara.

A thousand years ago Sahara salt was literally worth its weight in gold, so the deposits at Taoudenni in what's now northern Mali must have been quite a find.

In Timbuktu I started looking for a guide and some camels of my own. This proved quite easy - Timbuktu is that sort of place - and soon I signed up with U Batna, an Arabic speaking Moor who was the proud owner of three good-looking beasts.

U Batna was from one of the nomadic families who grazed sheep and goats on the spiky desert grass around Timbuktu, wrapped in his desert robes and turban scanning the horizon and puffing on his cow-bone pipe - he looked the perfect Lawrence of Arabia.

I could not speak Arabic but as the trip progressed he taught me all the words I needed to understand like "camel", "sand", "thirsty" and "keep walking".

There was no road - we just headed due north. Fodder for the camels was always a problem, and sometimes we would keep going long into the night looking for it, finally stopping to cook rice on camel-dung campfires and sleep under the stars.

On the other hand water was never a worry. As everyone knows, a camel can survive for a month without water, and I found that it can also carry up to 80 litres for its human companions - either in leather pouches (nicely traditional, but leaky) or in more watertight inner tubes from old car tyres.

After three weeks we arrived at Taoudenni and I was utterly shocked. This community of 120 men, one of the remotest on earth, had no houses, no fresh water, no medicines, no electricity, no telephone - not even any cooking fuel apart from camel dung.

A camel carcass lay putrefying in the open air. At this time of year, daytime temperatures are in the upper 30s Celsius. In summer they can reach 50 - that's more than a 120 degrees Fahrenheit. It is a posting from Hell.

But amazingly I found the salt miners friendly and happy to talk.

In medieval times they would have been slaves. Then in the 1960s they were political prisoners; now they are mostly self-employed desperadoes just trying to pay off debts.

I watched them hacking out the salt from a few feet under the surface, using crude axes in pits they had dug by hand.

On a good day a strong miner can produce perhaps eight 40 pound slabs, which the camel-drivers pay for in the time-honoured way by delivering one slab in every four to the miner's house in Timbuktu.

The markup in price between Taoudenni and Timbuktu is what gives both miners and camel-drivers a living.

If all goes well, a top-grade slab will fetch أ‚آ£1.60 ($3) at the pit but four times this in Timbuktu.

But it does not always go well. When a camel bolts or is badly loaded the slabs get broken, greatly reducing their value. If one of the broken ones has been earmarked for a miner's house, that is the one that gets delivered. The camel-drivers pay no compensation - in fact no money changes hands at all.

Until lately the miners had no choice but to accept this unfair system, but now there is an alternative in the form of big lorries that have started to cross the desert.

A camel takes a month to make the round trip to Taoudenni - the lorries can do it in a week.

From the miners' point of view the lorry operators pay less per slab, but they pay on collection so cover the risk of breakages themselves. More importantly, they pay cash.

From Timbuktu the salt is shipped up the River Niger to the port of Mopti, where Moorish traders sell it on to people from a wide swathe of West Africa.

After saying my farewells to U Batna I joined one of the longboats, which are called "pinasses", and as we tied up on the Mopti waterfront I wondered about the future of the salt caravans.

Camels have the edge on lorries in that they do not need filling up with expensive diesel fuel.

This allows the caravans to bring in a decent profit and - literally - give the trucks a run for their money.

But will U Batna's sons and grandsons want to spend their lives coaxing these cantankerous animals across one of the most dangerous deserts on earth?