London Telegraph 
Tuesday, Oct 6th, 2009
MI5 warned the government that Osama bin Laden was planning an attack in the weeks leading up to September 11, including the morning itself, a new history of the Security Service discloses.
Newly published memos disclose an escalating concern about the terrorist leader right up until the moment he launched his attacks on the World Trade Centre in New York and the Pentagon in Washington killing nearly 3,000 people.
But the files also reveal that MI5 discounted the threat from Islamic extremism just six years before the attacks and did not believe that America was vulnerable.
The author of the book, Defence of the Realm, has been given access to all of MI5’s files dating back to its foundation in October 1909 in the first authorised history of an intelligence service anywhere in the world.
In a memo from July 6 2001, MI5 said the increase in the number of reports were “sufficient to conclude that UBL [Osama bin Laden] and those that share his agenda are currently well advanced in operational planning for a number of major attacks on western interests.”