He was just a friend. So I had no great expectations of the meeting we arranged in a quiet West End bar. I was just expecting a convivial drink, with the usual exchange of gossip, the catching-up on how our lives were going.

Almost immediately it was clear that this time it would be something more. The place was empty, but my friend chose the most secluded spot he could find. He was clearly nervous.

He wasn’t sure if I’d be interested in what he had, he said. It was about the run-up to the war. “All the Butler stuff,” he said, referring to Lord Butler, who had reported on the failures of intelligence over Iraq.

He thrust two sheets of paper into my hand. It was a “Secret — Strictly Personal” letter from Jack Straw to the prime minister written in March 2002, a year before the invasion.

In the letter the foreign secretary said there was no evidence that Saddam Hussein had any weapons of mass destruction worth talking about and that, in part as a result of a lack of US preparation, post-war Iraq was likely to become a very nasty place.

It was, in short, remarkably prescient and would make a pretty good story, I said, with some understatement. Well, I’ve got five others just like it from the same period, said my source. “Most say stuff just like that, or worse.”

The documents covered the period running up to a summit between George W Bush and Tony Blair at the president’s ranch in Crawford, Texas, in early April 2002. At that time the swift victory against the Taliban in Afghanistan had left hawks in the US administration openly briefing that Iraq was next.

Most of the leaked documents were designed to brief ministers or Blair on whether backing the US plans to get rid of Saddam would be sensible and legal. They set out the merits and dangers of taking part. Their gist was that there weren’t many merits. The documents made it pretty clear that it wasn’t sensible, it wasn’t legal and it was very risky.

The document that seemed to encapsulate the problems was another “Secret — Strictly Personal” letter to Blair. It was written by his foreign policy adviser, Sir David Manning.

“I think there is a real risk that the (US) administration underestimates the difficulties,” Manning wrote. “They may agree that failure isn’t an option, but this does not mean that they will avoid it.”

When I reported these documents I was surprised to find that there was no real interest in them in America. The story swiftly died away.

Then eight months later, in the run-up to Britain’s general election, with the focus on the attorney-general’s advice to Blair on the legality of war, somebody else gave me further, even more startling documents. They concerned a meeting in Downing Street on July 23, 2002, eight months before the invasion, when Blair was insisting to the public that all options on Iraq were still open.

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