Throughout 2001 the US authorities were being given warnings that a terror attack was imminent. A Congressional Commission, FBI officers and the CIA were all worried. There were even specific warnings about planes being flown into buildings. Louise Hidalgo spoke to former Senator Gary Hart who co-chaired the Congressional Commission that tried to convince the government to take action.

This programme is a rebroadcast.

Photo: Smoke pours from the World Trade Centre after it was hit by two passenger planes on September 11, 2001 in New York City. (Credit: Robert Giroux/Getty Images)