The Independent makes no apologies for returning this week to a forensic analysis of the events leading up to the 2003 Iraq invasion. Though it is almost eight years since the fall of Baghdad (and the main British protagonist, Tony Blair, left office more than three-and-a-half years ago) there remains a powerful public interest in getting to the bottom of how this country ended up in this most disastrous of foreign adventures.

We learned this week, courtesy of the Chilcot inquiry, that Mr Blair's public assertions in January 2003 that Britain could legally attack Iraq without a second United Nations resolution was not compatible with the advice he had been given by the Attorney General, Lord Goldsmith. That is the sort of information – Mr Blair disregarding the clear advice of the government's own top lawyer – that could have brought down the Prime Minister if it had been widely known in 2003. At the very least it would have been deeply destabilising for the government as it locked Britain into American preparations for invasion.

The Chilcot inquiry would inform us better if it could. Yesterday we learned that Sir Gus O'Donnell, head of the Civil Service, has vetoed attempts by Sir John Chilcot to publish documents recording conversations between Mr Blair and President George Bush in those crucial days.

This is deeply regrettable. Sir Gus argues that future prime ministers will not speak freely to US presidents if this correspondence is made available now. That seems overly fastidious. The Chilcot panel has seen the documents and clearly feels there is a public interest in their release.

And so there is. There is a public interest in learning from Mr Blair's mistakes, from the loose manner in which he made the case for war, to his slippery attitude to legal advice, to his supine stance before a US president intent, come what may, on invasion.