By Rob Watson, BBC World Service, Political Correspondent
It promises to be history in the making. For the first time ever a former prime minister will find himself defending his decision to go to war live on television and for that matter live on the web and on radio too.
He will be doing so in front of the Chilcot Inquiry - named after its chairman the retired civil servant Sir John Chilcot.
It was set up by the government after pressure from the families of those killed and the opposition parties. The government's hope no doubt was to quietly park the issue until after the general election but it has not worked out that way.
Since the inquiry began last November its televised hearings featuring a parade of officials, soldiers, spies and politicians have often made front page news, as witnesses discussed the events leading up to and after the invasion.
Generals have complained about the lack of planning, diplomats about the wisdom of going to war and lawyers about its legality.
There have of course been powerful defences of the decision too. But all roads have been leading to Tony Blair, the man who was ultimately responsible for taking that decision.
Mr Blair is expected to make the most robust defence of all and those close to the former prime minister say he remains confident what he did was right.
To judge from the hearings so far the panel are likely to question him closely about when and why he agreed to support President Bush and whether he misrepresented the intelligence case against Iraq.
No-one is expecting him to stumble. But beyond the obvious of drama of it all, does Mr Blair's appearance have any wider significance?
Certainly it seems unlikely to change many peoples minds about the Iraq war, either for or against.
There have after all been four previous inquiries and the topic is now less toxic following the withdrawal of British troops last summer.
But the government fears Mr Blair's and Iraq's return to the headlines will remind the voters in Britain of a deeply unpopular war just months before the general election.