UK Boosts Terror Alert Level Second-highest designation means attack 'highly likely' By M. Morris, Newser Staff Posted Jan 22, 2010 5:56 PM CST 10 comments Comments Police officers patrol near Parliament in London, April 10, 2009. The UK terror alert level was raised today to the second-highest designation, which means an attack is highly likely. (AP Photo/Kirsty Wigglesworth) (Newser) – The British government raised its terror threat level to the second-highest designation today, signifying that an attack is "highly likely"—but officials swiftly added that terrorist aggression is not considered imminent. The upgrade from "substantial" means Brits must be "more aware," the Home Secretary said. "We still face a real and serious threat to the UK from international terrorism," said Alan Johnson, who declined to link the elevated scrutiny to the attempted downing of a Detroit-bound airliner on Christmas Day. "We never say what the intelligence is and it would be pretty daft of us to do that," he explained. "It shouldn't be thought to be linked to Detroit or anywhere else for that matter." London will play host next week to two conferences on Afghanistan and Yemen—where Al-Qaeda in the Arabian Peninsula has been stepping up operations recently, the BBC notes. And direct flights from Yemen are no longer permitted to enter the UK because of security concerns.