I want to know the answer to the following question:
What did the Ministry of Home Security fail to discover?
All the background I'm provided with is that "But the great bulk of the traffic went on; and Londoners—though they glanced apprehensively each morning at the list of closed stretches of line displayed at their local station, or made strange detours round back streets in the buses—still got to work.". Is that enough to answer the question?
Answer: no