"An informal system has been in place, which might be thought of as a precursor to Detachment 2701, or 2702 or whatever we are calling it," Alan says. "When we want to sink a convoy, we send out an observation plane first. It is ostensibly an observation plane. Of course, to observe is not its real duty—we already know exactly where the convoy is. Its real duty is to be observed —that is, to fly close enough to the convoy that it will be noticed by the lookouts on the ships. The ships will then send out a radio message to the effect that they have been sighted by an Allied observation plane. Then, when we come round and sink them, the Germans will not find it suspicious—at least, not quite so monstrously suspicious that we knew exactly where to go."