On July 1 the world’s attention was on Baghdad. Three days after the Americans had formally handed power to an interim Iraqi government, Saddam Hussein was due in court to face charges of war crimes and genocide.

When Ehsan Karim left home that Thursday morning, however, he had other things on his mind. A little-known government accountant, Karim was in charge of the Iraqi supreme audit board. Not obviously a frontline job, it would nonetheless cost him his life.

After trawling through the financial records of Saddam’s former regime, Karim had uncovered evidence of a multi-billion-dollar global web of deceit and corruption.

Among the meticulous files left by the dictator’s British-trained civil service were voluminous details of the scandalous operations of the United Nations oil for food programme, which was set up to stop Iraqis from starving but had become Saddam’s private bank.

The biggest humanitarian programme in history, it nominally allowed his regime to sell Iraqi oil to buy essential supplies under UN supervision. For years Saddam had systematically abused it to fill his own treasury and to reward foreign friends and helpful governments. The records appeared to implicate some of the most powerful figures on the planet.

The names of various alleged beneficiaries had already come out unofficially, although fiercely challenged. What Karim appeared to have unearthed was the smoking gun. He had briefed American politicians on his findings. Now he was due to give his first media interview to The New York Times.

According to a friend, however, Karim was a troubled man. He felt that he was being denied the whole picture.

As usual he left home at 8am in a chauffeur-driven black Mercedes with a bodyguard, unaware that a sophisticated bomb had been placed in a parked car on his route to the finance ministry.

The driver and the bodyguard died instantly, but Karim was dragged alive from the wreckage and taken to hospital. Initial reports said he was only slightly hurt.

The attack did not make headlines. Iraq — and the world — was focused on the astonishing courtroom pictures of a chained, bearded Saddam scoffing arrogantly in the shadow of the gallows.

Even when Karim died from his injuries that evening — and Ansar al-Sunnah, a militant Sunni group with purported links to Al-Qaeda, claimed responsibility for the murder — he remained a footnote to other news.

The public remained ignorant of Karim’s significance and of what he had found. Now, however, the secret is not only out but is being used to refight the political battles of the Iraq war. Senior American politicians are accusing France and Russia of “contempt and greed” and charging the UN with connivance in the channelling of funds to terrorists.

As critics conflate the many strands of the oil for food scandal into a full-blown conspiracy, questions are being asked about the meticulous assassination of the obscure Iraqi accountant. Was his death the work of a foreign government about to be embarrassed by his findings or could it have been orchestrated by figures in the new Iraqi regime haunted by their past? Did the CIA want to keep the lid on Karim’s evidence to protect friendly Middle Eastern countries heavily implicated in the scandal?