Plans to exploit Iraq's oil reserves were discussed by British Government ministers and the world's largest oil companies the year before the country took a leading role in invading Iraq, Government documents show.
Revealed for the first time, the papers raise new questions over Britain's involvement in the war, which had divided then Prime Minister Tony Blair's Cabinet and was voted through only after he claimed Saddam Hussein had weapons of mass destruction.
The minutes of a series of meetings between ministers and senior oil executives are at odds with denials of self-interest from oil companies and Western Governments at the time.
The documents were not offered as evidence in the ongoing Chilcot Inquiry into the UK's involvement in the Iraq war. In March 2003, just before Britain went to war, Shell denounced reports it had held talks with the UK about Iraqi oil as "highly inaccurate".
BP denied having any "strategic interest" in Iraq, while Blair described "the oil conspiracy theory" as "the most absurd".
But documents from October and November the previous year paint a very different picture.
Five months before the March 2003 invasion, Baroness Symons, then the Trade Minister, told BP that the Government believed British energy firms should be given a share of Iraq's enormous oil and gas reserves as a reward for Blair's military commitment to the United States' plans for regime change.
The papers show Symons agreed to lobby the Bush Administration on BP's behalf because the oil giant feared it was being "locked out" of deals that Washington was quietly striking with US, French and Russian Governments and their energy firms.
Minutes of a meeting with BP, Shell and BG (formerly British Gas) on October 31, 2002, read: "Baroness Symons agreed that it would be difficult to justify British companies losing out in Iraq in that way if the UK had itself been a conspicuous supporter of the US Government throughout the crisis."
The minister then promised to "report back to the companies before Christmas" on her lobbying efforts.
The Foreign Office invited BP in on November 6, 2002 to talk about opportunities in Iraq "post regime change". Its minutes state: "Iraq is the big oil prospect. BP is desperate to get in there and anxious that political deals should not deny them the opportunity."
After another meeting, this one in October 2002, the Foreign Office's Middle East director at the time, Edward Chaplin, noted: "Shell and BP could not afford not to have a stake in [Iraq] for the sake of their long-term future ... We were determined to get a fair slice of the action for UK companies in a post-Saddam Iraq."
While BP was insisting in public that it had "no strategic interest" in Iraq, in private it told the Foreign Office that Iraq was "more important than anything we've seen for a long time".
BP was concerned that if the US allowed TotalFinaElf's existing contact with Saddam Hussein to stand after the invasion it would make the French conglomerate the world's leading oil company. BP told the Government it was willing to take "big risks" to get a share of the Iraqi reserves, the second largest in the world.
Over 1000 documents were obtained under Freedom of Information over five years by the oil campaigner Greg Muttitt. They reveal that at least five meetings were held between civil servants, ministers and BP and Shell in late 2002.
The 20-year contracts signed in the wake of the invasion were the largest in the history of the oil industry. They covered half of Iraq's reserves - 60 billion barrels of oil, bought up by companies such as BP and CNPC (China National Petroleum Company), whose joint consortium alone stands to make US$658 million profit a year from the Rumaila field in southern Iraq.
Last week, Iraq raised its oil output to the highest level for almost a decade, 2.7 million barrels a day - seen as especially important at the moment, given the regional volatility and loss of Libyan output.
Muttitt, whose book Fuel on Fire is published next week, said: "Before the war, the Government went to great lengths to insist it had no interest in Iraq's oil. These documents provide the evidence that give the lie to those claims.
"We see that oil was in fact one of the Government's most important strategic considerations, and it secretly colluded with oil companies to give them access to that huge prize."
Conservative estimates put about 115 billion barrels of oil beneath the Iraqi desert, ranking the country fourth in the global league table behind Saudi Arabia, Canada and Iran.
But even that staggering number does little to explain just how much oil Iraq might be sitting on.
According to the US Energy Information Administration, the 115 billion barrel figure is a best guess based largely on unsophisticated seismic data, most of which dates back nearly 30 years. Geologists believe the real figure could be 45 to 100 billion barrels higher.
The country has produced between 2.4 and 2.6 million barrels since the 2003 invasion, making Iraq the 10th biggest oil producer.
BP penned a memorandum of understanding in 2005 to provide technical assistance at the huge Rumalia field in southern Iraq, in which it holds a 39 per cent stake. Within five years BP is hoping to triple output to 2.85 million barrels per day, accounting for 3 per cent of global annual output.
Royal Dutch Shell's major interest is a stake in the 8.6 billion barrel West Qurna field, to the north of Rumalia, which it shares with ExxonMobil and NOC, an Iraqi company. It also has an interest in the potentially 12.6 billion barrel Majnoon field.
Total, the French giant, holds a stake in the Halfaya field, which holds a mere 4.1 billion barrels at the best estimate. Other "majors" from Brazil, Norway, Kazakhstan and a host of other countries also have rights to vast pools of Iraqi oil.
WHAT THEY SAID
Foreign Office memo, November 13, 2002, following meeting with BP: "Iraq is the big oil prospect. BP are desperate to get in there and anxious that political deals should not deny them the opportunity to compete. The long-term potential is enormous."
British Prime Minister Tony Blair, February 6, 2003: "The oil conspiracy theory is honestly one of the most absurd when you analyse it. The fact is that, if the oil that Iraq has were our concern, I mean we could probably cut a deal with Saddam tomorrow in relation to the oil. It's not the oil that is the issue, it is the weapons ... "
BP, March 12, 2003: "We have no strategic interest in Iraq. If whoever comes to power wants Western involvement post the war, if there is a war, all we have ever said is that it should be on a level playing field."
Shell, March 12, 2003: "We have neither sought nor attended meetings with officials in the UK Government on the subject of Iraq."