WSJ:
British antiterrorism chief Peter Clarke said at a news conference that the plot was foiled because "a large number of people" had been under surveillance, with police monitoring "spending, travel and communications."
Let's emphasize that again: The plot was foiled because a large number of people were under surveillance concerning their spending, travel and communications. Which leads us to wonder if Scotland Yard would have succeeded if the ACLU or the New York Times had first learned the details of such surveillance programs.