The key points of the Iraq war inquiry explained

Gordon Brown has given evidence to the Iraq inquiry about his involvement in the decision to go to war and the funding he authorised, as chancellor, for troops and equipment.

What did Mr Brown say?

During the four-hour session, the prime minister said he fully backed the 2003 war but said lessons could be learned from it, particularly over post-war reconstruction. He said he had been kept "in the loop" by the then prime minister Tony Blair in the build-up but said he had largely restricted his involvement to financial matters, assuring Mr Blair from an early stage that he would not attempt to block military options "on the grounds of cost". In the most public scrutiny yet of his views about the controversial conflict, he denied starving UK armed forces of equipment - insisting that every request made while he was chancellor was met. He expressed "sadness" for the deaths of British troops and Iraqi citizens during the conflict.

What was the reaction to his performance?

Families of British personnel killed in Iraq said Mr Brown's evidence had not allayed their concerns that their loved ones may have been sent to war without being properly equipped. Opposition parties accused Mr Brown of being "evasive" over funding for the conflict and the armed forces in general, and of answering the questions he wanted to hear, rather than those actually put to him.

Wasn't Brown due to appear after the general election?

The inquiry initially said the prime minister and other ministers with ongoing responsibility for Iraq would appear after the election. However, after pressure from the opposition, Mr Brown made clear he would be willing to appear at any time.

What is the remit of the inquiry?

It is looking at events between 2001 and 2009, covering the decision to go to war, whether troops were properly prepared, how the conflict was conducted and what planning there was for its aftermath. Ministers say the terms of reference are unprecedented in their breadth while inquiry chairman Sir John Chilcot says he will not shirk from apportioning blame where he sees fit. 179 British service personnel were killed in Iraq between 2003 and 2009. Tens of thousands of Iraqi civilians died over the period, though estimates vary considerably.

Who else has given evidence so far?

The highlight of the inquiry, so far, was former prime minister Tony Blair's appearance in January. Other senior ministers in the run-up to the war, including former Foreign Secretary Jack Straw, Defence Secretary Geoff Hoon and International Development Secretary Clare Short have also appeared. The inquiry has taken evidence from a Foreign Office lawyer who quit in protest at the war and from Lord Goldsmith, the former attorney general who advised ministers that the war was lawful. It has also heard from senior diplomats, civil servants and military commanders involved in the build-up to war and the military campaign.

What were the key moments during Tony Blair's evidence?

The former prime minister faced six hours of questioning in the first public scrutiny of his decision to take the UK to war against Iraq. Mr Blair said he had no regrets about removing Saddam Hussein as he posed a threat to global security. He denied giving any private assurances to President Bush that he would support military action come what may and insisted that disarming Saddam, not regime change in itself, was the reason for sending UK troops into battle.

What are witnesses being asked about?

Areas covered include the development of UK policy towards Iraq between 2001 and 2003 and UK-US relations over the period. There has been scrutiny of the intelligence available on weapons of mass destruction in Iraq and its influence on decisions taken by ministers as well as events at the UN in the run-up to war, including the negotiation of UN resolution 1441. This gave Iraq a "final opportunity" to disarm and co-operate with weapons inspectors or face "serious consequences". There has also been significant focus on the legal arguments surrounding the war and whether it was justified without explicit UN authorisation.

Are witnesses testifying on oath?

No they are not, leading some to question the merits of the inquiry. However, all those appearing have been asked to sign a piece of paper saying they gave a "full and truthful" account of events. There is also controversy over the powers of the panel. There are no judges nor QCs on the body, leading many to question whether it has the expertise to question whether the war was legal. But the panel says it will call on relevant legal advice where needed.

What are proving to be the controversial points?

Critics of the Iraq war argue the Bush administration had effectively decided to remove Saddam Hussein by force by the middle of 2002, that the UK was aware of this and had offered its support. Former Prime Minister Tony Blair denied this but Sir Christopher Meyer, the UK's man in Washington at the time, highlighted in his evidence a private meeting between the two men in April 2002, after which Mr Blair began to talk publicly about regime change. Sir David Manning said Mr Blair signalled his intention to back regime change but urged President Bush to get UN authorisation for it. Alastair Campbell said Mr Blair wrote private notes, as yet unpublished, to President Bush during 2002 suggesting the UK would ultimately take part in military action if diplomatic efforts failed.

How did the inquiry begin?

The inquiry officially began in July. Sir John and the four other panel members met some of the families of the 179 UK personnel killed in Iraq between 2003 and 2009 as well as former and current serving personnel. During the meetings, several relatives of those killed criticised the decision to go to war, saying the British people had been lied to about the threat posed by Iraq. Sir John and his fellow panel members also spent weeks examining thousands of relevant documents from across government. However, there has been criticism that some documents have not been declassified, meaning that although the inquiry can view them they cannot be made public.

Can the public see the hearings?

Sir John has said it is "essential" that as much of the inquiry as possible is held in public. Gordon Brown was heavily criticised for initially suggesting it would mainly take place in private, for national security reasons. In what critics said was an embarrassing U-turn, he later said it was up to Sir John to decide how it should proceed. Hearings are taking place in public unless there are compelling reasons of national security not to do so. Currently there has been just one private session with General Sir John Reith, the commander who oversaw the invasion.

This is not the first inquiry into Iraq, is it?

No. There have already been four separate inquiries into aspects of the Iraq conflict. In 2003, the Commons Foreign Affairs Committee and the joint Parliamentary Intelligence and Security Committee both looked into the intelligence used to justify the war. The Hutton inquiry, in January 2004, examined the circumstances surrounding the death of scientist and weapons adviser Dr David Kelly. The Butler inquiry, in July 2004, looked once again at the intelligence which was used to justify the war.

How long will the latest probe take?

After Foreign Secretary David Miliband gives evidence on Monday, the hearings will be suspended until after the general election - expected to be held in May. Hearings will resume in the summer with the inquiry's final report expected to be published in late 2010 or early 2011.