Britain's terrorist threat level was raised tonight from “substantial” to “severe” - meaning that counter-terrorism agencies believe an attack is “highly likely”.
The measure was approved at a meeting of the Government’s Cobra emergency committee and announced by Alan Johnson, the Home Secretary.
The Times understands that the decision to raise the threat level is connected to the conference on Afghanistan taking place at Lancaster Gate, London, next Thursday.
Sources said there had been intensive discussions throughout the day relating to intelligence suggesting a possible attempted “spectacular” by an al-Qaeda affiliated group.
But the shift was also described by one source as “precautionary” rather than rooted in any firm information that an identified terror cell was plotting an attack.