Sergeant "Smudge" Smith looks out over an undulating riverbed on the south-western outskirts of Kabul and ponders who might be hiding among its darkening ridges.

"You could drive a four-tonne truck down there and not see it. Imagine the difficulty in spotting a column of 20 men," says the burly soldier from the Royal Anglian Regiment, one of more than 1,500 British troops assigned to maintain security in this battered city.

The evening light is fast fading, the crumbling mud buildings behind the patrol are filled with shadows. The threat of hidden enemies appears to grow closer. Last week, just here, a British squad took fire from an unseen and so far unidentified force. Later on this night, UK soldiers were to come under shotgun fire from the roof of a house.

While Kabul remains largely calm, the approach of a council to determine the next government has raised tensions. There have been warnings of plots against the interim administration and foreigners. Early yesterday, a rocket was fired over the top of the international peacekeeping brigade in eastern Kabul - it bounced to a halt, unexploded, by an unsuspecting cow.

In the village of Barjay, the site of the patrol, there have been two gruesome murders and the ethnic Hazara residents are frightened. Locals, who welcome the British troops, say that fundamentalist forces are not far away. "We have suspicions there are key players who are directing activities in this area," says Lt Col Neal Peckham.

But to the men of B company, assigned to patrol the area, this is why they joined up. "I like to help here: these people's lives are all jumbled," comments Arajah Cambridge, a 29-year-old former cruise-line bartender from St Vincent, in the Caribbean, as he advances - surrounded by children - through a dusty street. "I'm never nervous, never scared. If it's gonna happen, it's gonna happen."

The Anglians have flooded Barjay with extra troops and established a forward base in its police station, causing some consternation to the local constables, according to Sgt Smith, but compensated for by a gift of boiled sweets.

Further back in B company headquarters, known as "Suffolk House", the soldiers have settled in to an old barracks next to a wall of rusting cars. In a dormitory that smells of wet towels, teenage troops relax in cots surrounded by pictures of topless women, sporting weapons. "Sacha with an AT4 disposable LAW, Andrea with an RPG7 launcher, 85mm" explains the motif to a page of Guns and Girls, published by a former Royal Anglian captain.

They listen to Tracy Chapman on a decrepit tape player, read books by Andy McNab, the former special forces serviceman, and play five-card stud. A small gym has been set up. On patrol they appear calm, friendly and professional. Using skills developed in Northern Ireland, the men fan out and scan buildings for danger.

Each wears a flak jacket with plates covering the heart, carries an SA-80, has night vision equipment, and is in constant radio contact with his colleagues - some perched in observation posts atop the surrounding hills.

Even so, the enemy knows these gulleys and backstreets well, and even the highest tech equipment is not perfect. A couple of soldiers have fallen down deep holes in the ground.

While the locals are friendly now, and the streets mostly calm, the Royal Anglians are well aware of the fate of their regimental predecessors when the tide turned against them in the first Afghan war in the mid-19th century. Of 16,000 who tried to escape from Kabul through Afghanistan's narrow passes, only one made it through. "We don't like to discuss it too much," says Sgt Maj Andy Buxton.