"Now, if ten convoys are sent out and all of them are sunk, even those under cover of clouds and darkness, the Germans will ask themselves how we knew where those convoys could be found. They will realize that we have penetrated the Enigma cypher, and change it, and then this tool will be lost to us. It is safe to say that Mr. Churchill will be displeased by such an outcome." The Main Guy looks at all of the others, who nod knowingly. Waterhouse gets the feeling that Mr. Churchill has been bearing down rather hard on this particular point.