Britain's latest inquiry into the invasion of Iraq has begun, and Sir John Chilcot, who shows every sign of recognising the need to address the war's unanswered questions, has promised his probe will be "rigorous, fair and frank".

Previous reports on the war had limited scope, but Chilcot's remit begins in 2001, so the extent to which the invasion was a reaction to 11 September may become clear - as may how much control of British foreign policy was handed to the US by a prime minister determined to stand "shoulder to shoulder" with George Bush.

On the first day of hearings, Sir Peter Ricketts, chair of the Joint Intelligence Committee in 2001, said there had been concern on both sides of the Atlantic that "containment" of Saddam Hussein was "failing" - and that "regime change" was being discussed. The inquiry will very likely consider the context of the 14 March 2002 memo in which Blair's former foreign policy adviser David Manning wrote to him after dining with Condoleezza Rice:

“I said that you would not budge in your support for regime change but you had to manage a press, a parliament and a public opinion that was very different than anything in the States." Yet in February 2003, on the eve of war, Blair told the House of Commons: "I detest [Hussein's] regime, but even now he could save it by complying with the UN's demands." To do its job, the inquiry will have to shed light on that contradiction.