'The transition between two addresses or even a change in the type of transport is a vulnerable time for a subject, providing the surveillance professional with a good opportunity to observe. A man's home is his castle, and often people will remain safely behind their walls for hours, out of the camera's reach. With few clues about the impending departure of a subject, it can often catch the hunter unawares when the person darts out and away into the traffic. If there is a garage door, for example, to slow their departure, it is far easier, as there will be a warning sign that movement is imminent.'