Tony Blair’s belief in himself and his powers of persuasion emerge as one of the key reasons why the UK went to war in Iraq.

The Chilcot Report concludes that at times the former Prime Minister, who led Labour to a record three general election victories, "over-estimated" his ability to win over US President George Bush.

The document also appears to warn that future leaders should guard against Mr Blair’s self-belief.

Under a section marked Lessons, it notes: “When the potential for military action arises, the government should not commit to a firm political objective before it is clear it can be achieved. Regular reassessment is essential.”

Again and again the theme emerges in the document, which is a critique not just of Mr Blair but of his whole system of government.

Much mocked at the time, when the young Labour leader was elected in 1997 he almost immediately eschewed the formality of the cabinet system.

Instead, he adopted a more informal approach with his cabinet ministers.

This caused two phrases to enter political discussion, “sofa government” and “call me Tony”.

But the more casual tone was to have serious consequences in the run up to, operation of and aftermath of the Iraq War.

The report suggests that the then Prime Minister failed to understand the "importance of collective ministerial discussion".

Critically this allows ideas and policies to be challenged and examined more closely.

Again and again the report warns that intelligence, assumptions, proposals and even crucial legal advice went unquestioned.

Among these were the 'flawed' reports that Mr Blair received about Iraq's potential for Weapons of Mass Destruction (WMD), which led to his now notorious 45 minutes claim.

His judgment that Iraq had breached the terms of a United Nations Security Council resolution, providing legal justification for UK involvement in war, was delivered in a "perfunctory" note without discussion in Cabinet and without a formal record of how it had been reached, the inquiry found.

The legal advice itself had been changed at the last minute by the then Attorney General Lord Goldsmith, after he initially suggested that war would be illegal.

The report found: "Given the gravity of this decision, Cabinet should have been made aware of the legal uncertainties" and that Lord Goldsmith should have been asked to provide written advice setting out the Government's position and the risks involved.

The process that led to the decision on the war's legality was “far from satisfactory”.

It was also far from the only one.

Time and time again the report finds occasions when policy should have been considered by a cabinet committee, and then by the cabinet itself, but was not.

At one point, the inquiry found: “There were no substantive discussions of the military options, despite promises by Mr Blair.”

The report also concludes: “Mr Blair did not seek and did not receive considered advice from across Government specifically examining whether the evidence (for war) was ‘sufficiently compelling’ to provide the basis for a judgement of this magnitude and seriousness.”

On specific issues, such as over the military planning for the invasion and its effects, he appears to have been unable to exert control over his own ministers.

In one damning section, the report says: "Whitehall departments and their ministers failed to put collective weight behind the task. In practice, the UK's most consistent strategic objective in relation to Iraq was to reduce the level of its deployed forces."

The inquiry also dismissed Mr Blair's claims that he could not have known how difficult post-invasion Iraq would become.

It found that the Government's war preparations "failed to take into account the magnitude of the task of stabilising, administering and reconstructing Iraq".

In a passage that will re-ignite accusations that he was the US's "poodle" the report also warned that the the US -UK special relationship has proved "strong enough to bear the weight of honest disagreement" and "does not require unconditional support where our interests or judgments differ".

And yet the picture that emerges is one of a man over-confident in his ability to persuade the Americans to his point of view, on issues such as another possible UN resolution and others, even as he gets closer and closer to war.

The probe has been led, for seven long years, by Sir John Chilcot, a former Whitehall mandarin.

From the start of his mammoth task he made clear that his inquiry would make no judgement on whether or not the invasion decision was legal in terms of international law.

That question can only be resolved by a court, he has said.

He stuck to that pledge in the document he produced yesterday.

It concluded that the inquiry "has not expressed a view on whether military action was legal. That could of course only be resolved by a properly constituted and recognised court".

"We have however concluded that the circumstances on which it was decided there was a legal basis for UK military action were far from satisfactory."

Instead of a legal decision, Sir John promised that his report would provide a "full and insightful" account of the decision-making that led to the invasion of Iraq in 2003.

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