The long-awaited Chilcot report has finally been published today. It comes during a very tumultuous time in British politics - and while its publication was always going to be fractious, it remains to be seen how the Tories - and more interestingly, Labour, use it to their advantage.

The 12-volume report, which is 2.6 million words long and can be found here, will be dissected over the coming days, but here's a quick summary of some of the key statements from it:

Key points

The report concludes that the UK chose to join the invasion of Iraq before the peaceful options for disarmament had been exhausted. Military action at that time was not a last resort.

It suggests that 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.

Despite explicit warnings, the consequences of the invasion were underestimated. The planning and preparations for Iraq after Saddam Hussein were wholly inadequate. Blair 'did not establish clear Ministerial oversight of US planning and preparation. He did not ensure that there was a flexible, realistic and fully resourced plan that integrated UK military and civilian contributions, and addressed the known risks.'

The government failed to achieve its stated objectives. In the absence of a majority in support of military action, the report considers that the UK was, in fact, undermining the Security Council’s authority.

Blair's 24 September statement to the House of Commons contained judgements about Iraq’s capability that were presented ‘with a certainty that was not justified’.

Legality of Invasion

The report doesn't express view of legality of military action. That can only be resolved by a properly constituted court.

However, it concludes that the circumstances in which it was decided that there was a legal basis for UK military action were far from satisfactory.

WMDs, British intelligence and the threat from Saddam

The report presents an assessment of Iraq's WMDs and how they were presented to support the case for military intervention.

Report highlights 'ingrained beliefs' of UK policy and intelligence: Iraq had retained some chemical and biological capabilities; was determined to preserve and enhance them; including a nuclear capability; was able to conceal activity from UN inspectors.

24 September 2002, Mr Blair presented potential threat of WMDS from Iraq in House of Commons. This judgement and the dossier published the same day were presented with an unjustifiable certainty.

Chilcot goes into some detail about Blair's presentation of Iraq's WMDs and nuclear capacity.

Formal decision to invade Iraq

After Saddam failed to accept US ultimatum to leave within 48 hours, the cabinet made the decision to invade on 17 March 2003. This was supported by Parliament in a vote the following day.

Chilcot then sets out how decision was shaped by Blair and his government of the previous 18 months: Blair encouraged Bush not to take hasty action on Iraq post-9/11, but suggested that they should work on a 'clever strategy' for regime change. Blair and President Bush met at Crawford, Texas in April 2002. Plan was still to contain Saddam, but UK mindset had changed: Joint intelligence Committee concluded that Hussein couldn't be removed without invasion. Government had stated that Iraq was a threat. It had to disarm or be disarmed. Implied use of force if Iraq didn't comply. Internal contingency planning for a large contribution to military operation had begun. 28 July- Blair wrote to Bush assuring his supported 'whatever' happened, but he demanded change in three areas in return: Progress on Middle East Peace Process, UN authority and shift in public opinion in UK, Europe and Arab world. 8 November, resolution 1441 adopted by Security council. Iraq had final opportunity to disarm or face 'serious consequences.' Weapons inspector returns to Iraq. However, during December, Bush decided that inspections wouldn't be enough and the US military would take action in early 2003. Blair agrees to US timetable for action. 12 March - clear there was no chance of securing majority support for second UN resolution before US took action.

In the absence of a majority in support of military action, the report considers that the UK was, in fact, undermining the security council's authority.

Shortcomings in planning and preparation

Despite promises that Cabinet would discuss the military contribution, it did not discuss the military options or their implications.

When the invasion began, UK policy rested on an assumption that there would be a well-executed US-led and UN-authorised operation in a relatively benign security environment.

Blair 'did not establish clear Ministerial oversight of US planning and preparation. He did not ensure that there was a flexible, realistic and fully resourced plan that integrated UK military and civilian contributions, and addressed the known risks.'

Between early 2002 and the invasion of Iraq in March 2003, Blair received warnings about:

The significance of the post-conflict phase as the 'strategically decisive' phase of the engagement in Iraq […] and the risk that a badly handled aftermath would make intervention a 'net failure';

The likelihood of internal conflict in Iraq, the potential scale of the political, social, economic and security challenge;

The need for an analysis of whether the benefits of military action outweighed the risk of a protracted and costly nation-building exercise;

The absence of credible US plans for the immediate post-conflict period and the subsequent reconstruction of Iraq;

The need to agree with the US the nature of the UK contribution to those plans;

The importance of - UN authorisation for the military occupation of Iraq, without which there would be no legal cover for certain post-conflict tasks.

Yet when Blair set out the UK’s vision for the future of Iraq in the House of Commons on 18 March 2003, no assessment had been made of whether that vision was achievable, no agreement had been reached with the US on a workable post-conflict plan, UN authorisation had not yet been secured, and there had been no decision on the UN’s role in post-conflict Iraq.

Blair did not:

- Establish clear Ministerial oversight of post-conflict strategy, planning and preparation;

- Ensure that ministers took the decisions needed to prepare a flexible, realistic and fully resourced plan integrating UK military and civilian contributions;

- Seek adequate assurances that the UK was in a position to meet its likely obligations in Iraq;

- Insist that the UK’s strategic objectives for Iraq were tested against anything other than the best case: a well-planned and executed US-led and UN-authorised post-conflict operation in a relatively benign security environment;

- Press President Bush for definitive assurances about US post-conflict plans or set out clearly to him the strategic risk in underestimating the post-conflict challenge or failing adequately to prepare for the task;

- Consider, or seek advice on, whether the absence of a satisfactory plan was a sufficient threat to UK strategic objectives to require a reassessment of the terms of the UK engagement in Iraq. Despite concerns about the state of US planning, he did not make agreement on a satisfactory post-conflict plan a condition of UK participation in military action.

There were no instructions on how to establish a safe and secure environment if lawlessness broke out as anticipated.

The failures in the planning and preparations continued to have an effect after the invasion.

The Blair-Bush relationship

A personal note from Blair to President Bush 2 June 2003 is included, which reads: 'But the task is absolutely awesome and I’m not at all sure we’re geared for it. This is worse than re-building a country from scratch. We start from a really backward position. In time, it can be sorted. But time counts against us… My sense is: we’re going to get there but not quickly enough. And if it falls apart, everything falls apart in the region.'

Chilcot rejected the view that the UK would lose diplomatic influence if it had refused to join the war. 'Blair was right to weigh the possible consequences for the wider alliance with the US very carefully. But 'If the UK had refused to join the US in the war it would not have led to a fundamental or lasting change in the UK’s relationship with the US.'

Post-conflict period

The government’s preparations failed to take account of the magnitude of the task of stabilising, administering and reconstructing Iraq, and of the responsibilities which were likely to fall to the UK.

The scale of the UK effort in post-conflict Iraq never matched the scale of the challenge. Whitehall departments and their ministers failed to put collective weight behind the task.

Military intervention elsewhere may be required in the future. A vital purpose of the Inquiry is to identify what lessons should be learned from experience in Iraq.

The gap between the ambitious objectives with which the UK entered Iraq and the resources that the Government was prepared to commit to the task was substantial from the start. Even with more resources it would have been difficult to achieve those objectives, as a result of the circumstances of the invasion, the lack of international support, the inadequacy of planning and preparation, and the inability to deliver law and order. The lack of security hampered progress at every turn. It is therefore not surprising that, despite the considerable efforts made by UK civilian and military personnel over this period, the results were meagre.

The Inquiry has not been able to identify alternative approaches that would have guaranteed greater success in the circumstances of March 2003. What can be said if that a number of opportunities for the sort of candid reappraisal of policies that would have better aligned objectives and resources did not take place. There was no serious consideration of more radical options, such as an early withdrawal or else a substantial increase in effort. The Inquiry has identified a number of moments, especially during the first year of the Occupation, when it would have been possible to conduct a substantial reappraisal. None took place.

The UK failed to plan or prepare for the major reconstruction programme required in Iraq. Many of the failures which affected pre-invasion planning and preparation persisted throughout the post-conflict period. They included poor inter-departmental co-ordination, inadequate civilian military co-operation and a failure to use resources coherently.

Although the UK expected to be involved in Iraq for a lengthy period after the conflict, the Government was unprepared for the role in which the UK found itself from April 2003. Much of what went wrong stemmed from that lack of preparation.

Conclusions:

Military action in Iraq might have been necessary at some point. But in March 2003:

There was no imminent threat from Saddam Hussein.

The strategy of containment could have been adapted and continued for some time.

The majority of the security council supported continuing UN inspections and monitoring.

The vital purpose of the report is to identify what lessons should be learnt from this experience. Lessons include:

Blair overestimated ability to influence US decisions on Iraq.

UK-US relationship is strong enough to bear the weight of honest disagreement.

Importance of collective ministerial discussion which encourages frank and informed debate and challenge.

Need to assess risks, weigh options and set and achievable and realistic strategy.

Vital role of ministerial leadership and co-ordination of government activity.

Need to ensure that civilian and military arms of government are properly equipped.

Most important lesson - 'all aspects of any intervention need to be calculated, debated and challenged with the utmost rigour.'