Sir Michael Wood, the most senior legal adviser at the Foreign Office at the time of the Iraq invasion, told the Chilcot Inquiry into the Iraq war that he disagreed with the advice of Lord Goldsmith, the former attorney general, that military intervention was lawful.
In a written statement he said:
"I considered that the use of force against Iraq in March 2003 was contrary to international law."
Sir Michael also wrote to Jack Straw on January 24 2003 outlining his concerns with comments Straw made to then-US vice president Dick Cheney in Washington.
Straw told Cheney that Britain would "prefer" a second resolution, but it would be "OK" if they tried and failed to get one "a la Kosovo".
Sir Michael wrote:
"I hope there is no doubt in anyone's mind that, without a further decision of the Council, and absent extraordinary circumstances of which at present there is no sign, the UK cannot lawfully use force against Iraq to ensure compliance with its Security Council WMD resolution."
Straw rejected the advice, on the basis the international law was very vague.
The government of the day was looking for ways to justify and enact a decision that it had already been made. The alleged "vagueness" of international law gave them what they thought to be a hook onto which to hang their arguments, albeit ever so tenuous.