A former MI6 intelligence officer issued a chilling warning that a major terror attack on the scale of 9/11 or the 7/7 London bombings could strike at any time, according to a report by The Sun. Ex-spy Aimen Dean claimed hundreds of Al-Qaeda sleeper agents are quietly operating across the UK, waiting to unleash mass-casualty attacks. He said the threat is no longer about “if, but when,” alleging Iran hosted Al-Qaeda for decades and enabled sleeper networks in Britain. The warning comes as the U.S. steps up airstrikes against ISIS-linked targets in Nigeria and Syria.