Sant of the Secret Service by William Le Queux

Mr Easterbrook soon found himself comfortably ensconced in a large room, and surrounded by a staff, every single member of which, though he little suspected it, was in the direct employ of the Special Branch. Few suspects have ever been subjected to such microscopic scrutiny. He literally could not make a single movement unobserved. He was constantly shadowed in and out of his office by agents who were relieved every few hours; inside his house Madame Gabrielle was incessantly on the watch. And in the meantime we prepared for him the trap which proved his undoing.

One day Mr Easterbrook found awaiting his attention a number of copies of an "urgent" and "strictly confidential" memorandum which gave in elaborate detail the plan of a naval operation which for sheer dare-devilry was enough to take one's breath away. Needless to say, it was "spoof" from beginning to end. But it was spoof so thoroughly plausible in its conception, and so artistically worked out in its wealth of detail, that it might well have deceived someone far better versed than Herr Estbruck in naval matters. I had the privilege of going over it with the distinguished naval officers who drew it up, and I can hear to-day the roars of laughter with which it was received by the company of experts gathered to listen to the elaborate joke. Of course the men who really knew detected the imposture at once; to the novice the plan looked like the details of a gigantic attack on one of Germany's strongest naval bases.