It's been seven years in the making and has cost taxpayers £10 million, but the long-awaited report into the controversial Iraq War will finally be published on Wednesday 6th July.
But what is it and why does it matter?
What is the Chilcot report?
The inquiry into the Iraq War was set up in 2009 by then Prime Minister Gordon Brown to investigate the UK's involvement in Iraq.
It was tasked with examining almost a decade of decisions from 2001 to 2009.
This included: the decision to go to war, whether British troops were adequately prepared, the military action, what planning there was for the aftermath and what lessons can be learned.
It soon became known as the Chilcot Inquiry after its chairman Sir John Chilcot, a retired civil servant.
When and why did Britain go to war in Iraq?
Britain joined the US-led invasion of Iraq in March 2003 with troops tasked with removing leader Saddam Hussein from power and disarming the country of its weapons of mass destruction.
But the UK's participation was extremely controversial.
A total of 179 British soldiers were killed and tens of thousands of Iraqi civilians died during the conflict and no evidence of weapons of mass destruction was found despite Blair's warning.
Millions of people took to the streets of London to protest against the war and the military action also led to the resignations of several members of the Labour government.
Despite a significant rebellion from Labour MPs, the House of Commons authorised Blair's plan for war 72 hours before military action was launched.
Blair failed to secure United Nations backing for military action, which has since sparked debate about whether the invasion was lawful or not.
How long will the report be and what time will it be released?
It will be very, very long - it is expected to contain 2.6 million words, span 12 volumes and include an executive summary.
Journalists will be given access to the full report early in the morning but will not be able to report on what it says until Sir John Chilcot finishes speaking at around 11am.
Anyone who wishes to buy a full copy will have to pay nearly £800.
Families of the British soldiers who died will not have to pay for a copy.
Why has it taken so long?
When he announced the start of the inquiry, Gordon Brown told the Commons that "it will take a year".
But it dragged on and on - lasting longer than British troops were actually in Iraq.
The panel massively underestimated the scope of the inquiry and the time it would take to study 150,000 documents.
The Maxwellisation process - where those criticised are given the chance to respond - also caused delays.
Another reason was disagreements between the government and the inquiry panel about what classified material could be published - this included messages between Tony Blair and US President George W Bush.
The illness and then death of panel member Sir Martin Gilbert also delayed proceedings.
The long delay angered bereaved families - some of whom threatened legal action - and politicians.
Prime Minister David Cameron told Sir John Chilcot last year that he was "fast losing patience" over the time taken to publish.
Who gave evidence to the inquiry?
More than 150 people gave evidence to the inquiry with Tony Blair the most high-profile witness.
Blair, who appeared twice before the panel, expressed "deep and profound regret" about the loss of life suffered by British troops and Iraqi civilians.
But he vigorously defended his decision to lead Britain into war, saying he had "no regrets" about removing Hussein from power and would take the same decision again.
The inquiry also heard from senior Labour ministers including former Foreign Secretary Jack Straw, Defence Secretary Geoff Hoon and International Development Secretary Clare Short.
Alastair Campbell, Tony Blair's former communications chief, insisted he would defend "every single word" of the 2002 dossier on Iraq's weapons of mass destruction, which included the claim that weapons could be launched within 45 minutes.
Former UN arms inspector Dr Hans Blix also appeared, telling the inquiry that he believed the war was illegal.
What will the political consequences be?
The Iraq War has divided the Labour Party for over a decade and with the party currently in turmoil, the report could have a major impact on its future.
Jeremy Corbyn, the current Labour leader, was a vocal critic of the war and speculation suggests he may even go as far as accusing his predecessor Blair of war crimes - a move that will undoubtedly cause further division in the party.
It has also been suggested that Corbyn wants to "crucify Blair" for the war and apologise on behalf of his party before he steps down in the face of growing pressure from his own MPs.
Whatever the report says, it is bound to send shockwaves across Westminster.