Nigel Morris: How Mr Blair and Mr Straw abandoned law for politics...

A picture emerged of warnings being brushed aside at the highest levels

The three former ministers feeling the most intense heat over the legality of the Iraq war – Tony Blair, Jack Straw and Peter Goldsmith – are qualified lawyers. Mr Blair and Mr Straw abandoned the law for politics, while Lord Goldsmith combined both careers in his role as Attorney General.

The politicians' apparent determination to override the unanimous opinion of Foreign Office lawyers is the most dramatic disclosure so far at the Chilcot hearings, and Elizabeth Wilmshurst made no effort yesterday to disguise her opinion of her former political master's expertise.

Asked whether she believed Mr Straw's view had been influenced by his legal qualifications, she replied acidly: "He is not an international lawyer."

On the 31st day of hearings, a picture emerged of warnings that the invasion had no basis in international law being brushed aside at the government's highest levels.

Sir Michael Wood, the senior legal adviser at the Foreign Office, said his arguments were rejected out of hand when he advised Mr Straw that war could not be justified without a fresh UN resolution.

He told him in a memo two months before the war: "To use force without Security Council authority would amount to a crime of aggression." Mr Straw wrote back: "I note your advice but I do not accept it." Sir Michael said yesterday: "He took the view that I was being very dogmatic and that international law was pretty vague and that he wasn't used to people taking such a firm position."

His version of events provided a striking contrast to Mr Straw's portrayal last week of his "reluctance" to go to war and fears over its illegality. Documents released to the inquiry yesterday also made plain that Downing Street was left in no doubt over its lawyers' worries. Lord Goldsmith initially told Mr Blair's chief of staff, Jonathan Powell, that he was "pessimistic" that the legal basis existed for military action. But Mr Straw argued for a legal interpretation "which coincides with our policy intention".

Lord Goldsmith eventually reversed his legal advice just three days before tanks crossed into Iraq. Today he will face intense pressure to explain the factors that led him to change his mind. Without his legal approval, it would have been politically impossible for Mr Blair to win backing from the Commons for the invasion.

The former prime minister will be asked by the Chilcot team on Friday whether Downing Street bullied his Attorney General into line – or deliberately delayed seeking his advice. He will be challenged over Ms Wilmshurst's accusation that Number 10 treated winning legal backing for the war as secondary to pressing ahead with military preparations.

As for Mr Straw, who returns to the Chilcot inquiry next month, he will face questions over whether – despite his protestations to the contrary – he took the key role in removing the legal barriers to war.