A portable electronic device comprises a display on a first, front side of the device, a touch sensitive surface on a second, rear side of the device substantially opposite the first side having a similar shape and orientation to the display, and a touch input mapping means arranged to map a position of a detected touch on the touch sensitive surface to a position on the display and, a tapping detection means. The tapping detection means is arranged in operation to detect a tap as when there has been a loss and reacquisition of touch from a user on the touch sensitive surface. And the tapping detection means is arranged in operation to detect the position of the detected tap on the touch sensitive surface as being the position at which touch was lost.