Explosive evidence showing the Government was "clearly advised" the Iraq war was illegal will be disclosed at the Chilcot inquiry just days before Tony Blair gives evidence, it has been reported.
Sir Michael Wood, who was the Foreign Office's chief legal adviser, is expected to reveal he believed the war was unlawful without a second United Nations resolution.
Elizabeth Wilmshurst, a senior FCO lawyer who quit in protest at the invasion, will also tell the inquiry that she was not "a voice in the wilderness" in harbouring doubts over the legitimacy of military action, the Independent on Sunday reported.
She is expected to claim Sir Michael told then attorney general Lord Goldsmith of his reservations days before the attack on Baghdad began in 2003.
Philippe Sands QC, an expert on the legality of the war, told the paper the inquiry had received documentary evidence of Sir Michael's reservations - but is yet to publish it.
Ms Wilmshurst became the only UK civil servant to quit over the war when she resigned before the first attacks on Iraq, telling her superiors that an invasion without UN sanction would be a "crime of aggression".
Professor Sands, director of the Centre on International Courts and Tribunals at University College London, said both of the FCO's most senior legal advisers opposed the invasion.
He told the paper: "The inquiry has before it documentary evidence confirming the point that Michael saw the invasion as unlawful. It is more explicit than anything we have ever seen before."
Lord Goldsmith will appear at the inquiry on Thursday, 24 hours before Mr Blair.
As Mr Blair arrives at the Queen Elizabeth II Conference Centre, a delegation of protesters plan to give the "people's dossier" of questions to Sir John Chilcot.