Mr Mangold said: "Paul Greengrass who directed Matt Damon in The Bourne Supremacy is a friend of mine. He phoned me up and said that Matt Damon was playing Angleton in a film and he wanted to talk to me and he asked if he could come round."
The former Panorama journalist, who claims to have seen "every spy film ever made", said that Damon was "absolutely lovely and totally unselfconscious" during their three hour chat.
He added: "We talked a lot of Hollywood gossip and then we spoke about the CIA and what motivated Angleton."