According to the Havlish memorandum, Iran facilitated bin Laden’s move three years later to Afghanistan. An Iranian intelligence officer met bin Laden there at about the time he first discussed airborne suicide attacks on American cities. During the ensuing period, when bin Laden was using a satellite phone, 10 per cent of his outgoing calls were to Iran.

Al-Qaeda operatives received training in Iran in airline hijacking, according to the memorandum. Significance is given to a communication four months before 9/11, in which a leading Iranian intelligence official authorised support for “al-Qaeda’s future plans”. The communication emphasised that “no traces must be left…” and that activity was to be limited to “existing contacts” between bin Laden’s henchman Zawahiri and Hizbollah’s Mughniyah.

It was Mughniyah, the new court document states, who “accompanied some of the future ‘muscle hijackers’ ” [who would murder aircrew and subdue passengers] on flights into and out of Iran in October 2000; Mughniyah who flew to Beirut on the same plane as Ahmed al Ghamdi, a future hijacker on one of the planes that would crash into the Trade Center; and Mughniyah, too, who “visited Saudi Arabia to coordinate activities there”.