PHOTO CAPTION: "A second al-Qaeda terror cell is believed to be planning carnage in the UK." SNIPPET: "Senior security sources last night revealed they are hunting extremists aiming to bomb a location such as a nightclub or shopping centre. They believe the cell will target London rather than the North- West, where 11 men were arrested on Wednesday, as the capital holds more "international significance"." Evidence gleaned from the arrests was revealed to Cobra, Whitehall's emergency committee of intelligence chiefs and ministers.