The Serious Crimes Unit was regarded as one of the most corrupt elements of the British-mentored and trained constabulary in Iraq’s second city.

In Saddam Hussein’s time, local security forces dragged hundreds of people to the al-Jameat compound in the middle of the night. They were never heard of again. It became known as the “station of death”.

The two-storey building had been reopened by the British as a police station, part of the coalition’s optimistic attempts to restore order after Saddam’s overthrow.

Before long it was nicknamed “Gestapo HQ” by British officers. The horrors taking place behind its thick white walls were feared to compare with the sadistic excesses of the toppled dictatorship.

“When I visited the intelligence department at al-Jameat police station, I found prisoners stiff with fear, bound and gagged,” Stephen Grey, the journalist, wrote in the New Statesman.

No crime seemed too extreme for the unit, based at the police station in a once-pleasant middle-class neighbourhood. Its officers were blamed for death squad killings, extortion rackets and smuggling weapons from Iran.

They worked with the Tharallah criminal network to carry out contract killings and deadly roadside attacks on British forces using sophisticated imported technology.

By last year, dozens of Iraqis were being dragged from their homes, shot in the head and their bodies dumped in operations blamed on the unit.

The discovery of a body on the outskirts of Basra in April last year provided hard evidence that these police were out of control. The dead Iraqi had been arrested on suspicion of smuggling and gun-running. An examination of his remains showed that an electric drill had been used to penetrate his skull, hands and legs.

Britain ordered undercover troops to mount surveillance. The intelligence-gathering operation went wrong when two officers became involved in a shootout with plainclothes Iraqi police. The pair were arrested and taken to al-Jameat in September 2005. Under interrogation they were punched and kicked. This time the British forces would stand for no nonsense; they bulldozed the side of the police station. The men, who had been moved to a different location, were freed.

A 50-strong “al-Jameat Gang”, operating from the centre under cover of police uniform, was intimidating the remaining officers, who were too scared to inform on them.

Sheikh Ahmed al-Fartusi, a leader of the Shia Islamist al-Mahdi Army, had links to the group and was believed to provide them with protection in return for bomb-making equipment. He was seized by the international forces last year, part of a wave of arrests described as based on specific intelligence.

In an open letter to local people in January, John Cooper, commander of the British-led force in the south, described those arrested as “the most dangerous and corrupt people in Basra”. He said the Interior Ministry had “instructed the chief of police to remove the most dangerous and most rotten elements from the police”.

A year later, all hope of reforming the unit by weeding out rotten apples has been abandoned.

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