By Jonathan Head BBC Correspondent in Iraq

Already the city felt tense. Temperatures had soared to 50 degrees, and the humidity, carried by winds coming off the Shatt al-Arab river, was high.

It was unbearable to be outside in the day. And incessant gunfire between rival tribes kept us inside our hotel.

The troops are working amid a shattered infrastructure and unrest

Electricity is available only sporadically during the day.

People queued for several hours for petrol.

Outside the city, some electricity pylons lay crumpled on the ground, or upright but without cables - the result of deliberate sabotage, says the Coalition Provisional Authority.

This is the situation the British troops in Basra have to police.

We spent a morning with B company of the 1st Battalion, King's Regiment, patrolling al-Haritha, one of Basra's poorest and toughest neighbourhoods.

In command was Major Gary Dekin. He explained that after the riots last weekend his men had been patrolling in Warrior armoured vehicles.

People had been throwing stones, and worse, occasionally shooting or firing rocket-propelled grenades.

Plenty of complaints

On this morning he felt the mood had calmed enough to go in with Land-Rovers, though two Warriors would accompany us.

The neighbourhood warlord, Kadim Abed Ali, has his own private militia, and the British rely on him to sort out a lot of their security problems

Our first stop, outside a dusty collection of houses, was to hear the complaints of local residents. There were plenty.

They told Major Dekin there had been electricity for just four hours the night before, and there was little cooking gas available.

People had been chopping down date palms for fuel.

He told them his men were trying to fix the power, but it could take time.

To add to their problems, the area is disputed between two well-armed sheiks and has been subjected to fierce gun battles.

Major Dekin had locked both sheiks up until they agreed to stop their feud, but he was not optimistic about his chances.

'Corrupt and incompetent'

At B company's forward headquarters, where they are helping train a local police force, the soldiers live in cramped and stifling conditions.

In a small store room Sergeant Major Neil Rockcliffe showed me a formidable collection of weapons confiscated from local people.

We allow them to keep two weapons at home for their own protection - no sniper rifles or heavy machine-guns, though Sergeant Major Neil Rockcliffe

"We encourage them to own up to any weapons they have", he said.

"But we allow them to keep two weapons at home for their own protection - no sniper rifles or heavy machine-guns, though".

Next door, Major Dekin introduced me to the local police chief. They were all smiles together.

Later he told me he was going to sack the police chief at the end of the week, because he was incompetent and very corrupt.

He also introduced me to the neighbourhood warlord, Kadim Abed Ali, who is now the most influential politician.

He has his own private militia, and the British rely on him to sort out a lot of their security problems. He makes a useful friend, and a very dangerous enemy.

Stirring up trouble

Despite their best efforts, the young British soldiers face a formidable challenge in Basra.

Organised crime and gun-related violence have increased sharply.

Saddam loyalists, and possibly Islamic militants from neighbouring Iran, are moving into the poorer neighbourhoods, stirring up an already angry and frustrated population against the coalition.

The British need to prove they can be tough - but every time they kill to deal with armed opposition, they also risk starting blood-feuds with the local tribes.

These are very unpromising foundations for building a democratic Iraq.