Terror review: 'Smaller plot more difficult to detect'
17 July 2013 Last updated at 09:17 BST
The UK is facing new terrorist tactics, according to a report to be published on Wednesday.
The review by the Government's counter terrorism watchdog says that there has been a constant threat from Al-Qaeda since the 11 September attacks in 2001.
David Anderson QC examined the challenges faced by the police and security services.
He told BBC Breakfast that the "ultimate risk might not be as great, but a smaller and less organised plot is more difficult to detect".