The long-awaited, 2.6 million-word Chilcot report was published this morning, giving a comprehensive verdict on the UK's decision to go to war in Iraq.
Yesterday Sir John Chilcot said: "The main expectation that I have is that it will not be possible in future to engage in a military or indeed a diplomatic endeavour on such a scale and of such gravity without really careful challenge analysis and assessment and collective political judgement being applied to it.
"There are many lessons in the report but that probably is the central one for the future."
Here are some of the other key features.
Was the war legal?
The inquiry could not make a legal judgement.
However, Chilcot said: "We have, however, concluded that the circumstances in which it was decided that there was a legal basis for UK military action were far from satisfactory."
The report didn't find any evidence that the government influenced the content of the dossier claiming Iraq had weapons of mass destruction.
"There is no evidence that intelligence was improperly included in the dossier or that No.10 improperly influenced the text."
What did Blair say to Bush before the war?
The report says that Blair "undoubtedly influenced the president's decision to go to the UN Security Council in the autumn of 2002" - though notes he didn't succeed in changing the approach determined in Washington.
Yet, he also wrote a note to Bush in July 2002 trying to persuade him to build a coalition, which began:
“I will be with you, whatever. But this is the moment to assess bluntly the difficulties. The planning on this and the strategy are the toughest yet. This is not Kosovo. This is not Afghanistan. It is not even the Gulf War.
“The military part of this is hazardous but I will concentrate mainly on the political context for success.”
But Blair appears to have overestimated his ability to influence the US.
How much of the decision was based on poor intelligence?
The idea that Iraq "was a threat which had to be dealt with ... reflected the ingrained belief that Saddam Hussein’s regime retained chemical and biological warfare capabilities".
In the press conference, Chilcot said: "It is now clear that policy on Iraq was made on the basis of flawed intelligence and assessments. They were not challenged, and they should have been.
"The judgements about the severity of the threat posed by Iraq's weapons of mass destruction - WMD - were presented with a certainty that was not justified."
In the first place, or pre-conflict, the deployment of forces more quickly than anticipated meant there were "some serious equipment shortfalls when conflict began".
In post-conflict, UK forces faced gaps in key capability areas. It was not clear which person or department in the Ministry of Defence had responsibility.
"Delays in providing adequate medium weight Protected Patrol Vehicles (PPVs) and the failure to meet the needs of UK forces in MND(SE) for ISTAR and helicopters should not have been tolerated," according to the report.
"Although the Coalition had achieved the removal of a brutal regime which had defied the United Nations and which was seen as a threat to peace and security, it failed to achieve the goals it had set for a new Iraq. Faced with serious disorder in Iraq, aggravated by sectarian differences, the US and UK struggled to contain the situation. The lack of security impeded political, social and economic reconstruction."
Apparently, the UK thought the UN would would "administer and provide a framework for the reconstruction of post-conflict Iraq".
Chilcot today said: "Despite explicit warnings, the consequences of the invasion were underestimated. The planning and preparations for Iraq after Saddam Hussein were wholly inadequate"
Was war necessary?
"In the Inquiry’s view, the diplomatic options had not at that stage been exhausted. Military action was therefore not a last resort."