In written testimony before a special joint intelligence committee, the unnamed officer explained how he had warned his superiors in writing that “some day, somebody will die”, after being refused permission to locate Khalid al-Mihdhar and Nawaf al-Hazmi, both of whom were part of the hijack team that took over flight AA77 and crashed it into the Pentagon.

The two terrorists had entered America weeks before, despite being spotted in Malaysia at a meeting with other terrorists who had been implicated in the bombing of the USS Cole in Aden harbour in October 2000.

Their names were not immediately put onto official “watch lists” that could have prevented their entry.

At a key meeting in New York on June 11, 2001, the CIA did not pass on to the FBI information about the Malaysian meeting and its participants. It was only after the two men had entered America that they were belatedly put on the list and the FBI began looking for them.

Al-Mihdhar had given a false address on his visa application and could not be found immediately. The FBI officer asked for assistance from FBI headquarters but was told that his request for help in tracking down al-Mihdhar would breach the “wall” between intelligence and criminal investigations.

He wrote back on August 29: “Whatever has happened to this — some day someone will die — and wall or not, the public will not understand why we were not more effective and throwing every resource we had at certain ‘problems’. Let’s hope the FBI’s national security law unit will stand behind their decisions then, especially since the biggest threat to us now, Osama Bin Laden, is getting the most ‘protection’.”