I watched forces go in

I watched special forces from the Royal Marines secure the key Afghanistan airbase of Bagram early today and begin to prepare the way for a British peacekeeping force of more than 3,500.

Five British transport aircraft flew in to this airbase late last night, carrying 100 soldiers. Now the airbase, 15 miles north of Kabul, is sealed, the planes and soldiers parked on one side. There is tight security in place but I was able to get into the airport buildings.

The control tower, blasted and wrecked by previous wars, is already functioning again and is crowded with both British and Afghan soldiers.

A house nearby has five special forces men dressed in jeans and T-shirts and with black day packs. They are likely to be engaged in mine-clearing activities but at the moment they are lounging in the bright sunshine. erected for communications, and parked outside is a green dune buggy that taxi drivers around here would die for because of the bad roads.

The base is on maximum security alert and there is as edginess among the guards. One Afghan soldier on patrol saw me and insisted he escorted me to the airfield perimeter.

Then, as a jeep tried to enter, I heard two shots fired in the air. One soldier told me: "We do not want snoopers around. There could still be Taliban supporters out to cause trouble."

The airbase has the longest runway in Afghanistan and is shielded from Kabul by a mountain range.

The mood among the local troops is one of delight that the British are back on Afghani soil. One Afghan soldier, Edarat, said: "It is so nice to see the British come here. British or Americans, I don't mind which, both are my friends. Five planes came in last night. When I saw the British planes I thought 'the British are coming in, so the Taliban are definitely going out'."

Robert Fox writes: Tony Blair decided to order in British troops as tensions rose in Kabul itself between the Tajik leaders of the Jamiat Islami party of former president Burhanuddin Rabbani, who are accused of breaking agreements with the rest of the Northern Alliance and trying to take over Kabul and the government of Afghanistan.

The Jamiat spokesman Ahmad Walid Masood, brother of the guerrilla Ahmad Shah Masood blown up by a Bin Laden suicide squad on 9 September, has warned British and allied troops "to keep out of Kabul". Masood has been Afghanistan's ambassador to Britain, and sheltered in London during the Taliban dictatorship of his country.

"The Prime Minister is really up for this - and believes we have to go in now," said a senior British commander. Britain, Canada and France hope to have thousands of troops on the ground by Sunday night to help bring in aid and stabilise the Kabul area. The mission for the men of 2nd Battalion the Parachute Regiment and 45 Commando Royal Marines is primarily humanitarian. "They are not intended for offensive operations against the Taliban," said a Ministry of Defence official.

Specialist teams of the SAS, SBS and Special Patrols Troop of the Royal Marines are now believed to be involved in the hot pursuit of Osama bin Laden and Mullah Mohammad Omar, leader of the Taliban, in the south of the country. They are believed to have taken to the hills east of Kandahar, and may even be in Paktia province, from where they could escape into Pakistan.

The Taliban are continuing to put up stiff resistance in two main areas - Kunduz in the north and round Kandahar, the homeland of Mullah Omar, in the south. Attempts to negotiate a ceasefire in Kunduz appear to have failed because many of the 20,000 surrounded there are Uighurs fundamentalists from western China, members of the Uzbek Islamic movement allied to al Qaeda, as well as Arab and Chechen fighters from al Qaeda itself.

Men of 2nd Battalion the Parachute Regiment are leaving Colchester today for Oman and from there will fly straight to Bagram over the weekend. They will be joined by 45 Commando and elements of the headquarters of 3 Commando Brigade and 16 Air Assault Brigade.

Because of the size and vulnerability of Bagram airfield, the stabilisation force, as it will be called, is likely to require almost the full number of 4,000 troops the British government put on standby earlier this week. Bagram is a huge complex, built by the Russians in the eighties to fly strike aircraft all the year round and in all weathers. It is overlooked by high ground in which its is easy for teams of guerrillas to hide. Its distance of some 15 miles north of Kabul means it is secure form any tribal fighting that may break out in the capital - but it will mean allied troops will have to patrol and the routes form the base into the city.

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