Tony Blair is to be recalled before the Iraq Inquiry to answer questions over whether he pressured his Attorney General to change his advice on the legality of the war.
The former prime minister will face a second session before the Chilcot inquiry in the new year – a year after he refused to express regrets over leading Britain to war in 2003. His statement provoked fury in the hearing, with members of the audience calling him a "liar" and a "murderer".
The decision to summon him back will be a blow to Mr Blair, who had hoped his previous six-hour appearance would defuse the continuing controversy over the war.
But it is evidence that the Chilcot team believes there are still significant gaps to be filled as they try to piece together a full picture of the build-up to war. They are preparing to question him over suggestions that he put pressure on Lord Goldsmith, who was then the Attorney General, to alter his advice on the legality of the war. The lawyer's change of heart just before the planned invasion gave a green light for British troops to join the US-led military action.
Mr Blair has denied attempting to influence Lord Goldsmith, but previously classified papers showed he queried the Attorney General's previous view that invasion without a new United Nations resolution would be illegal.
He is also likely to face fresh cross-examination over the commitments he gave to President George Bush that Britain would back an invasion, as well as questions on weapons of mass destruction and whether he allowed proper debate in the Cabinet on the war.
Lord Goldsmith has been asked to provide further written evidence to the inquiry, which will hold its new round of public hearings in January and February.
Other witnesses who have been called back include Jack Straw, who was then Foreign Secretary, and the current Cabinet Secretary Sir Gus O'Donnell. But there is no recall for Gordon Brown, who gave evidence in March. Sir John Chilcot, the inquiry's chairman, said: "As we draft our report, it is clear that there are some areas where we need further detail.
"We will, therefore, be seeking further evidence on those matters. I am committed to taking the majority of this evidence in public."
Although the issue of Iraq is less toxic than when Labour was in power, Mr Blair's recall means police will have to mount a fresh security operation around the Queen Elizabeth II conference centre, where hearings are being held.
Anti-war protesters are seizing on the disclosure on the WikiLeaks website that Gordon Brown's government secretly promised to limit the extent of the Chilcot inquiry to prevent damage to the United States. The pledge was made last September as hearings got under way.
Lindsey German, convenor of the Stop The War Coalition, said Mr Blair would face another protest demonstration when he appears before the panel again. She said: "I hope this time that Chilcot will take a tougher attitude towards Blair. I really hope his evidence will be part of preparations for further action against Blair, hopefully in a court of law."
No date has been set for his second appearance before the five-strong Chilcot inquiry committee, which has been set down for half a day. But there will again be a public ballot for the 60 seats in the hearing room when he gives evidence. A third of the places will be set aside for families who lost relatives in the war.
What he will be asked
Were promises made to George Bush before the war?
Exactly what was said at a private dinner between Mr Blair and George Bush at the President's ranch in Crawford, Texas, in April 2002 – 11 months before the invasion? Sir Christopher Meyer, British ambassador to Washington at the time, suggested a deal was "signed in blood" that night. Mr Blair rejected the accusation – and was backed up by Jonathan Powell, his chief of staff, and Sir David Manning, his foreign policy adviser.
The war's legality
Much of the inquiry has focused on the belated change of heart by Lord Goldsmith, who was the Attorney General, over the legal justification for invading Iraq. When Mr Blair appeared before the Chilcot inquiry, his interrogators had a memo in which Lord Goldsmith warned of the danger of not having a fresh UN mandate for action. To their frustration, they could not ask about the memo as it was classified at the time, but the ban was lifted in July.
When did Mr Blair start to suspect that Saddam did not possess WMD?
He was robust in his defence of the flawed intelligence that made the case for war, but was not challenged on exactly when he realised no WMD would be found.