A "key moment" in the history of the Iraq war - was when President Bush asked Mr Blair to persuade his own vice president to go down the United Nations route, says Mr Campbell - who adds that he believes ex-ambassador Sir Christopher Meyer had been "churlish" in his own evidence on that meeting.
Had the PM committed himself to war by July 2002, asks Baroness Prashar. Mr Campbell says Mr Blair's instinct and leadership was to say "we should be with the Americans" but that did not mean tailoring British policies to meet US policy. "Did he share the means to that end (regime change)," asks Baroness Prashar. Ultimately, he did, says Mr Campbell - but he believed you had to exhaust the diplomatic route, with the threat of force behind it. Right up to the House of Commons vote Mr Blair was hopeful it could be resolved peacefully, he said.
George Bush said to Tony Blair there was "some planning going on", Mr Campbell recalls. He says before Crawford the PM had met the British military at Chequers to ask where they thought American thinking was at the time. He gave no commitment of British troops to George Bush at the Crawford summit in spring 2002, Mr Campbell says
After 11 September Tony Blair made clear his "genuine fear" of Weapons of Mass Destruction and failed states coming together, says Mr Campbell - an analysis he shared with the US. They also agreed Saddam's regime was "brutal". But Mr Blair made clear that British policy was to pursue disarmament, he insists
Removing Saddam had been US policy since Bill Clinton was president, he says - and adds that Mr Blair made clear the UK's objective was disarmament of Saddam Hussein through the UN. "George Bush wasn't sitting there saying we are about to go to war," he said.
Back to the meeting at George Bush's ranch in Crawford, Texas in 2002. Mr Campbell says he wasn't there for the meeting itself although he was at a dinner that evening - much of that discussion was about the Middle East crisis he says. On Iraq things were "recapped" - Mr Blair shared the US analysis of the threat posed by Saddam Hussein, Mr Campbell recalls.
Interesting news from the Dutch version the UK's Iraq inquiry. It has ruled that military action was not justified by UN resolutions on Iraq.
The Committee of Inquiry on Iraq
said security council resolutions did not "constitute a mandate for... intervention in 2003".
Mr Campbell is getting his own diary quoted back to him a lot. Baroness Prashar asks him what "concerns" were expressed in cabinet in March 2002 - he says he can't remember in detail but there were general concerns about whether there was a "rush to war - which there never was".
Baroness Prashar asks about the build-up to the Iraq war. Mr Campbell says he felt former ambassador Christopher Meyer's evidence to the inquiry, about a meeting between Tony Blair and George Bush in Texas in 2002, was not accurate. He says he does not accept there was a change at that meeting to a policy of regime change. Mr Blair was not saying at Crawford we now have a policy of regime change, he says. "I don't accept this analysis that at Crawford there was this fundamental shift in approach."
The questioning moves on from Sir Roderic. His fellow panel member Baroness Prashar asks if the cabinet secretary - the most senior civil servant - was involved in any of these meetings. Mr Campbell says he probably was as he was "in and out of Downing Street the whole time".
Was it unprecedented for a communications chief to have such a close relationship with the intelligence services asks Sir Roderic - Mr Campbell says he would have to ask his predecessors - he did not know. Sir Roderic suggests his role had not really existed in that form before - in terms of being very central in government. Mr Campbell says that is probably true.
Mr Campbell says he dealt with intelligence agencies during the period. Sir Roderic asks why he was included in a "very sensitive" meeting with two senior officers of the security services when it did not concern information that was publicly usable. Probably because Mr Blair wanted me to be, replies Mr Campbell. What about the "need to know" principle? Asks Sir Roderic - did Mr Campbell "need to know"? No, Mr Campbell concedes - but he says it was helpful.
Sir Roderic asks how closely Mr Campbell worked with the intelligence and security agencies. "At times very closely," says Mr Campbell. He says there was an intense period post-September 11 2001 and during the Iraq war. He says he did not "routinely see" intelligence reports and did not go out looking for them - but did have access to them.
Sir Roderic sums up Mr Campbell's role: "It effectively allowed you to range right across the board" in terms of government policy, he says - Mr Campbell agrees.
There were informal discussions and phone calls as well as the official Monday morning meetings. Were they formally recorded in terms of minutes, asks Sir Roderic. No, replies Mr Campbell, the calls could be about anything - including dealing with the media. He might e-mail other people if asked to do something like prepare a speech - or dictate it to his PA.
Some have suggested Sir Roderic, a former running partner of Mr Campbell might go easy on him but he keeps cutting him off mid flow to get Mr Campbell back onto the inquiry's remit. He has concentrated on asking about Mr Blair's inner circle of advisers and confidantes in the run-up to the Iraq war. Mr Campbell says there were a lot of people Mr Blair would speak to, in person or on the telephone. Admiral Boyce, John Scarlett, Jack Straw and Geoff Hoon - and Mr Campbell were at the formal Iraq meetings, he said.
Mr Campbell said Labour in 1997 inherited an outdated communications system from the Conservative government. Sir Roderic says that is before the timescale of the inquiry. Was Peter Mandelson in the inner circle of Iraq advisers, he asks? No, says Mr Campbell - but he says Gordon Brown was "one of the key ministers he would have spoken to regularly".
John Scarlett, Richard Dearlove, Jack Straw and Geoff Hoon were also important - as were Gordon Brown and John Prescott, Mr Campbell adds. Sally Morgan was key to his relations with the Labour Party. "I've never been a policy person," he says - Sir Roderic says he has previously said he was "involved in a lot of the policy discussions" about Iraq. Mr Campbell said he was, but as they related to "communications issues".
Sir Roderic asks how close Mr Campbell worked with Mr Blair. "Very," replies Mr Campbell, saying Mr Blair could not do the job alone and was dependent on political colleagues. Sir Roderic cuts him off and says, apart from him and Mr Powell, who was in Mr Blair's inner circle of advisers - Mr Cameron says David Manning was ahead of himself.
Sir Roderic says it was not just about dealing with the media - he quotes Mr Campbell's own diary back at him, and asks if he was there to do "whatever the prime minster asked you to do". Mr Campbell replies that he wouldn't have jumped off a building if Mr Blair asked him. "Be serious", says Sir Roderick.
First question from Sir Roderic Lyne - he asks if Mr Campbell was Mr Blair's longest serving close advisers. No, says Mr Campbell - suggesting Jonathan Powell might have been there longer. Sir Roderic asks what his actual role was - Mr Campbell said he worked with the PM and other officials to help devise and implement communications strategies. Pressed further he says he was also involved in political strategies.
Panel chairman Sir John Chilcot says they'll be looking at the presentation of the case for military action, including the drafting of the two dossiers among other things he says, admitting much is "familiar ground". No new documents will be declassified today, says Sir John.
And we're off. The panel are in their seats.
Mr Campbell is due to give evidence this morning from 1000 GMT to 1300 GMT. He's the only person before the inquiry today. Tony Blair will give evidence within weeks although the exact date is not known.
Mr Campbell's name has not cropped up at previous hearings but former MI6 chief Sir John Scarlett, at his appearance in December, denied being put under pressure to "firm up" the September 2002 dossier - which assessed weapons of mass destruction in Iraq. However he did point out that the foreword was written by Tony Blair, not him. Mr Campbell might be asked if he was involved in writing the foreword.
The BBC's Laura Kuenssberg said Mr Campbell looked relaxed when he arrived - despite being swamped by press as he got out of his car. He has already given evidence on Iraq twice - to the Commons foreign affairs committee and the Hutton inquiry. As well as being Tony Blair's communications director at the time, he was also one of the then PM's closest confidantes, she said.
Hello and welcome to our live coverage of today's Iraq inquiry hearing which will see Tony Blair's former communications director Alastair Campbell give evidence from 10am until 1pm. There have been several inquiries into aspects of the Iraq war before and this is not the first time Mr Campbell has given evidence. But this inquiry is the widest ranging and as this will be the first appearance by a major household name, a queue for seats at the hearing began forming early. You can watch it all live on this page, I'll be writing up all the key points as they happen plus bringing you the pick of analysis from BBC colleagues. We'll also include reactions from your emails and from coverage elsewhere on the web.