Days before the September 2002 dossier on Iraqi weapons that Tony Blair used to justify sending British troops to join the US in Iraq, an MI6 officer met with Iraq's head of intelligence and was told that Saddam Hussein had no active weapons of mass destruction, according to an investigative report by the BBC. The CIA had its own secret meeting in the months before the invasion, this one with Hussein's foreign minister, and was also told that Iraq had "virtually nothing" when it came to WMDs, according to the Guardian.
But MI6 and the CIA dismissed the intelligence, and the information was not passed along to relevant officials for subsequent inquiries. But, while dismissing information from high-level officials, MI6 stood by information gleaned from unreliable sources (such as the claim that Iraq was buying uranium from Niger) even after other intelligence agencies dismissed them, and MI6 and the CIA continued to take such claims seriously even after the sources were found to be unreliable. (More Iraq stories.)