After months of pressure from opponents, and a number of leaks, the government has published the full legal advice Attorney General Lord Goldsmith gave to the prime minister on the eve of the Iraq war. What is it all about?
Goldsmith's advice hardened within days
What is it all about?
The government's top legal adviser, Lord Goldsmith, said on the eve of the Iraq war, in a brief statement, that the UK would not be breaking international law. Opponents have long suspected that actually he had doubts about the war being legal.
What's happened now?
The government has published the lengthy advice that Lord Goldsmith gave to Tony Blair on 7 March 2003 - 10 days before the eve-of-war publication of the statement saying he believed the war was legal.
What did the attorney general say?
In his published advice just before Britain went to war, Lord Goldsmith gave a clear and unequivocal statement that the invasion of Iraq was legal.
But in his unpublished advice just 10 days before, he explained to Mr Blair that there were a number of difficulties in international law, and "the safest option" would be for Britain to secure a second UN resolution explicitly authorising war.
This is what Britain tried - but failed - to do in the intervening period.
Why does it matter?
Opponents claim that it was illegal to go to war without an explicit UN resolution authorising military action.
And they say the statement that the published advice was a "summary" of the detailed concerns outlined by the government's chief law officer was misleading.
They claim that if the Cabinet and MPs had known about the Attorney General's earlier advice, the country might not have voted to go to war.
Would it really have changed opinions?
Who knows? But even with the statement that the war was legal there was a major rebellion by Labour MPs in the war vote on 18 March 2003 - 139 Labour MPs opposed the war, and it was only the support of the Conservative Party that ensured a government majority.
Does international law matter?
There are varying views on that - but Mr Blair made clear that he would not be taking the UK to war if it was against international law. Military chiefs also made it clear that they could not have sent British troops into battle unless there was clear and unambiguous legal support for the war.
Would the other parties have acted differently ?
The Conservatives under Michael Howard now say that they would "have told the truth" to the British people and published the advice - but they still would have supported the war because they believe that the world is a better place without Saddam Hussein.
The Liberal Democrats opposed the war in Parliament in 2003 and still believe that Tony Blair made the wrong judgement in going to war.
Will Iraq matter in the election?
We should know the answer to that one on 6 May. Opinion polls show that the majority of voters are more concerned with bread-and-butter issues such as health and education than with the arguments as to why the country went to war in 2003.
But there is an important group of Labour voters, and Labour activists, who opposed the war - no-one quite knows how they are going to react when they come to vote. Or indeed if they are going to vote.
Opposition parties hope that by raising Iraq they will increase doubts in voters' minds about Mr Blair's trustworthiness.