Tony Blair is expected to strongly defend his decision to take the UK to war with Iraq when he appears before the Chilcot inquiry today.
He will be questioned for six hours on the build up to the 2003 invasion and its aftermath. This is the first time that he will give evidence in public.
Blair is expected to argue that even though Saddam Hussein did not possess weapons of mass destruction, he could have built them if military force had not been used.
He will insist that he acted in good faith, and that intervention was the right thing to do despite the high number of civilian causalities in Iraq.
Forty relatives of soldiers who died in the conflict will be present. A large demonstration is expected outside the Queen Elizabeth II centre in Westminster.