"Would the British let us send soldiers to take over their country?" The mood among the group of men on the banks of the Helmand River was menacing. All claimed to be Taleban fighters.

"If one Talib is in a village, the infidels bomb the whole village and kill innocent people," their leader went on.

"The British should come and fight us face to face and stop using their planes. They have been here three times and been nicely beaten three times," he added, referring to ill-fated British imperial adventures of the 19th and early 20th centuries.

"If there were two million foreign soldiers, we would defeat them if they fought us face to face."

British forces officially took over the volatile Taleban stronghold of Helmand yesterday for what the commander in charge admitted would be a "challenging mission".

The American Stars and Stripes was lowered at the main base in Lashkar Gar and the Union flag raised alongside the Afghan flag on another day of violence in south Afghanistan.

There are already frequent clashes: this week Afghan security forces said they had attacked Taleban militants in a cave complex north of Lashkar Gar, capital of the anarchic province of Helmand, where the deployment of 3500 British soldiers is gathering pace. Two Taleban fighters were said to have been killed and weapons seized.

The British-led Nato command structure known as the ARRC (Allied Rapid Reaction Corps) also started operating from Kabul on Monday. It is the first phase in a gradual integration of the entire foreign military presence in Afghanistan under Nato leadership.

By early next year, 14,000 United States soldiers will have been incorporated into the Nato force. A British lieutenant-general, David Richards, will command, the first time American forces have served under the theatre-wide leadership of a foreign general since World War II.

With a resurgent Taleban making inroads in the south, and growing disillusionment with the Western-backed Government of Hamid Karzai, Nato's Supreme Commander in Europe, US General James Jones, has called Afghanistan "the most important mission that Nato has undertaken" in its 58-year history.

What that might mean for ordinary British troops was evident in the lawless badlands of Helmand last week.

In the bazaar at Grishk, an area of noted Taleban sympathy in the north of the province, British Paras were patrolling the streets last week. In early February, close to the town, 200 Taleban fought Afghan forces backed by British Harrier jets.

Violence against British deployment has so far been limited to two suicide bomb attacks on successive Fridays this month, targeting the British base in Lashkar Gar.

On Friday, British squaddies guarding the gates of the headquarters did not appear unduly worried by their mission, although a lance-corporal who declined to be named admitted: "Everyone's parents are pretty worried."