Metropolitan Police Commissioner Sir John Stevens has urged the UK public to be vigilant to potential terrorist activity over the festive period. He said the activity and the actual threat has taken a "quantum leap" since September 11. Asked whether activity by the security services had prevented terrorist incidents over the last year, Sir John said: "That is absolutely right, there is no doubt about that. "The hard work has been successful, but we must not be complacent. We really must be vigilant," he said. Sir John was asked about comments by US homeland security director Tom Ridge, who warned...