The BBC's David Loyn has had exclusive access to Taleban forces mobilised against the British army in Helmand Province in southern Afghanistan.

There is no army on earth as mobile as the Taleban.

I remember it as their secret weapon when I travelled with them in the mid-1990s, as they swept aside rival mujahideen to take most of the country.

Piled into the back of open Toyota trucks, their vehicle of choice, and carrying no possessions other than their weapons, they can move nimbly.

The bare arid landscape of northern Helmand suits them well.

After one hair-raising race across the desert last week, patrolling the large area where they can move at will, they screamed to a stop at a river bank.

Hardy

It was sunset, and time to pray before breaking the Ramadan fast they had kept since sunrise.

Before praying, they washed in a dank-looking pool at the side of the almost-dry river bed.

Afghanistan has been in the grip of a severe drought for several years, but the lack of clean water does not seem to concern these hardy men.

We rose up and saved almost the whole country from the evils of corruption and corrupt commanders... that's why people are supporting the Taleban again now

Mohammed Anif

Taleban spokesman

They clean their teeth with sharpened sticks taken from trees, and sleep with only the thinnest shawls to cover them.

They have surprised the British by the ferocity of their fighting and their willingness to take casualties.

Their belief in the imminence of paradise means that few exhibit fear.

When we stopped for the night, they would break into groups to eat in different houses in a village.

They demand and get food and shelter from places where they stop, but it is impossible to say how enthusiastic the villagers really are.

Power base

These remote villages, scattered across the huge expanse of the northern Helmand desert, are very poor, and made poorer by the drought.

Taleban fighters appear both ferocious and fearless

The food we shared was just a bowl of rice, a vegetable stew made only of okra, and flat roughly-ground country bread.

The failure of aid policies to make a difference in southern Afghanistan and increasing corruption in the government and the national army, are spreading the power base of the Taleban.

The trucking companies, who backed them first in 1994 when they emerged to clear illegal checkpoints on the roads, are now backing them again.

This time the checkpoints are manned by Afghan government soldiers, who demand money at gunpoint from every driver.

The failure of the international community to stop this makes the military task of the British-led Nato force in the south much harder.

The Taleban official spokesman, Mohammed Anif, explained: "When the Islamic movement of the Taleban started in the first place, the main reason was because of concern among people about corruption.

"People were fed up with having to bribe governors, and other authorities.

"We rose up and saved almost the whole country from the evils of corruption and corrupt commanders. That's why people are supporting the Taleban again now."

Civilian casualties

The intensifying conflict itself also plays into their hands. It is hard for Nato to promote its mission as humanitarian given the inevitable civilian casualties of conflict.

The Taleban deny British claims that hundreds of their soldiers have been killed.

Sher and Nur Ahmad were orphaned when a bomb fell on their home

They say that since they wear only the loose long cotton shirts and trousers - shalwar kameez - of any local villager, then the British cannot easily tell them apart.

In a village damaged by a British attack on the night of 7 October, some people were too angry to talk to me because I was British.

One merely pointed to the torn and bloody women's clothing left in the ruins of the house and said bitterly, "Are these the kind of houses they have come to build - the kind where clothing is cut to pieces?".

Nato sources describe this village as being heavily defended by the Taleban, who fired on their forces throughout the operation.

British soldiers landed in helicopters, arrested a suspect and flew away.

But they left six dead in one family, including three young girls, and partially demolished the mosque.

Thousands of people have fled the fighting, many seeking refuge in Kandahar city, where they are putting severe pressure on the ability of the UN's World Food Programme to help.

They fear for the homes and farms they have left behind, and while not active Taleban supporters, it is clear that most blame Nato more for the worsening violence.

Folk memory

One man, Nazar Mohammed, now squatting with his family in a building site in Kandahar, said the Taleban have most to gain in the continuing conflict.

Nazar Mohammed says it is hard to cooperate with foreigners

"It's very obvious. Right now we see foreigners with tanks driving through our vineyards. They destroy people's orchards.

"They break through the walls and just drive across. When they take up positions in the village like this, nobody can cooperate with them."

There is one other factor that increases Taleban morale.

Few have any education beyond years spent in the madrassas, the fundamentalist religious schools in Pakistan that have produced an endless supply of Taleban for more than a decade.

But all know the story of Afghanistan's past victories over the British.

Engraved in their collective folk memory of Afghanistan's warrior history are tales of the defeat of the British in 1842 and 1880 along with the defeat of the Russians in the 1980s.

The Taleban disappeared to the mountains after their defeat in 2001, and found it hard to recruit.

Five years on they are back, and regrouping against an old enemy.