A directional display apparatus including a directional display device that is capable of directing a displayed image into a viewing window of variable width is provided with a privacy control function. A control system detects the presence of one or more secondary viewers in addition to a primary viewer, and decides whether the one or more secondary viewers is permitted to view the displayed image. The control system directs a displayed image into a viewing window which is adjusted, for example by decreasing the width, in dependence on that detection. In addition, the control system detects relative movement between the primary viewer and the display device, and the width of the viewing window is increased in response to detection of said relative movement.