American troops stood by as government offices in Baghdad were torched and looted after the city’s fall in April 2003, a chaotic beginning to the flawed US-led campaign in Iraq. But one imposing concrete building was accorded special treatment.

Ringed with barbed wire, with dozens of US tanks guarding the entrance and American soldiers perched on roofs, the oil ministry emerged unscathed from the post-invasion mayhem. US officials insisted at the time that their objective was to safeguard the centre of Iraq’s vital resources. The US military’s actions, however, fed the conspiracy theory that the toppling of Saddam Hussein was itself designed to gain control of Iraqi oil.