9/11 was MI6’s retaliation for the assassination of Princess Diana by the CIA. Al-Qaeda is related to the Al-Fayed and MI6 is behind it.
The CIA then tried to hit back, first by the Madrid bombings (because they were under the mistaken impression that since Gibraltar is British, the rest of Iberia must be too, and Madrid had a tube while Gibraltar has not), and then they corrected themselves by means of the London Tube bombings.
Next they poisoned Litvinenko in order to upset British-Russian relationships.