The long-awaited official report into the UK's involvement in the Iraq War is set to be published on Wednesday.

The report of the Iraq Inquiry, headed up by Sir John Chilcot, will run to over two million words.

Chilcot was appointed to lead the inquiry by Gordon Brown in 2009, shortly before he took over from Tony Blair as Prime Minister.

The inquiry was officially launched on July 30, 2009, and has heard 130 sessions of witness evidence and received around 150,000 documents.

Chilcot's remit included examining decisions made and actions taken in the lead-up to the March 2003 invasion and identifying lessons to be learned.

The report is expected to examine in detail the intelligence failure that led to the case for war being made based on false information.

The inquiry will also report on British involvement in the war itself from 2003 until 2009, when the last British troops left Iraq.

Chilcot has faced criticism for delays in producing the report, including rebukes from Prime Minister David Cameron as well as victims' families.

The report's publication has been delayed by a process called "Maxwellisation", under which those who may face criticism - believed to include former prime minister Tony Blair - are given the opportunity to respond before publication.

Relatives of the 179 British servicemen and women killed in Iraq during the war have also been given "early sight" of the report.

As chairman of the inquiry, Chilcot has been paid £790 a day since its launch. Other committee members have earned £565 a day.

Opening the inquiry in 2009, Gordon Brown said of the inquiry: "I am advised that it will take a year."

The Iraq Inquiry is estimated to have cost around £10m.