The inquiry into how Tony Blair committed Britain to war in Iraq is set to challenge the official version of events when it reports later this year, The Independent understands. The team led by Sir John Chilcot, which is examining Britain's part in the US-led invasion, will "challenge previous accounts of what happened", according to senior sources in the inquiry.
The prospect of a report which authoritatively confronts the established narrative from 2002 and 2003 – when Mr Blair sent 45,000 British troops into Iraq to overthrow Saddam Hussein – will unnerve many senior figures in Whitehall, and others who no longer operate at the heart of government.
By this May, the inquiry team expects to begin contacting those individuals who will be directly criticised in the Iraq report, to give them the chance to reply.
A decade after Britain's controversial role in the Iraq invasion, the Chilcot team has finally been shown a fuller account of communications between Mr Blair and the US President, George Bush, sources said.
The inquiry team believes that it "now knows what happened in the run-in to the war". Although it believes that the Government has handed over all the requested documents, negotiations continue with the Cabinet Office over what evidence can be fully cited when the report – which could number up to 3,000 pages – is published this autumn.
An inquiry source said: "After some previous problems, nothing is being withheld. However issues over declassification of some documents, and what evidence can be formally identified in the report, do remain."
The inquiry was ordered in June 2009 by the then Prime Minister, Gordon Brown.
Sir John Chilcot, a former diplomat who had previously investigated intelligence on Iraq's alleged weapons-of-mass-destruction arsenal as part of the Butler Review, was given a remit to look at events from early 2001, the run-up to the 2003 decision to go war, the subsequent military action and its aftermath, and to determine what lessons could be learnt.
Mr Brown had initially agreed to the Chilcot inquiry being held in private without any media reporting at all. However political opposition and wider accusations of pre-determined whitewash changed minds in Downing Street.
Public hearings began in November 2009 and ended in February 2011 with evidence taken from leading politicians including cabinet members involved in key decisions on Iraq, senior civil servants, legal advisers, intelligence personnel, military commanders and senior diplomats.
Last month, Mr Blair told the BBC in an interview to mark the 10th anniversary of the Iraq invasion that he had "long since given up trying to persuade people" that he had made the correct decision in 2003. He said he had been elected prime minister "to make these decisions".
The inquiry's focus on interpreting Mr Blair's own evidence – where he admitted he had not been constrained by the advice offered to him on the legality of the war by the former Attorney General, Lord Goldsmith – has remained a difficult hurdle to overcome.
Last year Sir John wrote to David Cameron saying that there remained difficulties with certain categories of evidence that still needed to be resolved. This included the "UK position in discussions between the Prime Minister and the heads of state or governments of other nations".
That was a subtle reference to the heated negotiations between the inquiry and the Cabinet Office over notes sent by Mr Blair to President Bush.
The negotiations also concerned diplomatically sensitive records of discussions between the two leaders in the crucial run-in to the March 2003 invasion.
Washington is understood to be "proactive" in finding out what evidence the UK government intends to allow to be published by the Iraq Inquiry.
Among the sensitive areas the US State Department want the report to avoid analysing in any detail are the origin and basis of comments by the Bush administration's former Treasury Secretary, Paul O'Neill, who said an attack on Iraq had been planned since Mr Bush's inauguration.
Although other material from the US has been seen by the Chilcot team, it is believed that few, if any, documents that have a US origin will be published in the final report.
Inquiry sources say that having established what happened with "a high degree of reliability", the task now facing Sir John and the inquiry team – Sir Roderic Lyne, the former UK ambassador to Russia, Sir Lawrence Freedman, professor of war studies at King's College London, and Baroness Prashar, a former member of Parliament's Joint Committee on Human Rights – is to decide "what we make of it all".
At the beginning of the investigation Sir John promised to get to the "heart of what happened" and said he would not avoid making direct criticism of individuals if it was justified.
Another member of the inquiry team, Sir Martin Gilbert, the celebrated biographer and historian who had been outspoken in his support of Tony Blair's decision to go to war, has been ill and is no longer able to take part in the inquiry's deliberations.
A final draft is expected to be ready in July.
Unanswered questions the Iraq Inquiry Report could resolve
In 2002 and 2003 Tony Blair and George W Bush held a series of bilateral meetings in Washington DC and at Camp David, which discussed Saddam Hussein and regime change in Iraq.
Q. Did Blair offer the US president assurances, without conditions, that Britain would support US military action in Iraq?
Legal advice from the then attorney general, Lord Goldsmith, is reported as having changed between March 7 and the eve of the invasion on March 17. The US foreign policy of wanting to remove Saddam had been official since 1998. But regime change was not legally sound in the UK.
Q. Was Blair’s assertion that Britain faced a “growing threat” from Saddam’s weapons of mass destruction, a convenient distortion of the military intelligence he was given because ‘regime change’ was not enough to justify war?
The UK’s intelligence community were not convinced by the information they were being presented with on Iraq’s alleged WMD arsenal. Downing Street was told by MI6 that their US counterparts were “fixing” the facts to fit George Bush’s anti-Saddam policy.
Q. Was Iraq an intelligence failure - or was Downing Street’s desire to control the interpretation of intelligence an abuse of power?
In the months running up to the March 2003 invasion, the progress and effectiveness of the UN –authorised weapons inspection teams inside Iraq were criticised by both Number 10 and the White House. Yet Blair said it was “beyond doubt” that Saddam had WMD and was attempting to develop a nuclear weapon.
Q. Was the United Nations’ monitoring and verification of Iraq’s compliance on WMD, deliberately weakened and side-lined by London and Washington in order to justify an invasion and subsequent regime change?
Throughout 2002 the UK government insisted that the issue of Saddam and disarmament could be resolved diplomatically. Though the US Defence Department were deep into preparations for war, the MoD in London avoided becoming involved in the logistics of organising an invasion force. The former defence secretary, Geoff Hoon, alleges that Blair refused to allow active preparation for war to encourage the diplomatic process.
Four years, 1m words: Inquiry timeline
June 2009 Gordon Brown announces an inquiry will be set up to "learn the lessons" of the Iraq war, led by former civil servant Sir John Chilcot.
November 2009 Former foreign office official Sir William Ehrman tells the inquiry that the UK received intelligence days before invading Iraq that Saddam Hussein may not have been able to use chemical weapons.
January 2010 Former Prime Minister Tony Blair's communications chief, Alastair Campbell, tells the Inquiry he would defend "every single word" of the 2002 dossier of Iraq's weapons of mass destruction.
January 2010 Tony Blair is questioned for six hours. He claims to have no regrets in removing Saddam and adds that there was no "conspiracy, deceit or deception" behind going to war.
July 2010 Evidence is taken from 35 people in private on the grounds of national security and international relations.
January 2011 Tony Blair is recalled and admits that the former Attorney General Lord Goldsmith could have been "more closely involved" in decision making before the war.
November 2011 The inquiry announces its findings will not be published until the summer of 2012, six months later than anticipated, only to be delayed again as it approaches a million words in length.