Former Prime Minster Tony Blair is preparing to be questioned in public for the first time about his decision to take Britain to war against Iraq.
In a much-anticipated appearance before the Iraq inquiry, he will be grilled for six hours on the build up to the 2003 invasion and its aftermath.
The panel is also likely to focus on the justification he gave for war in controversial government dossiers.
The session gets underway at 0930 GMT on Friday. Full coverage will be available on the BBC News website.
Nick Robinson reports.