A capacitive proximity sensor assembly comprises: (i) a capacitive proximity sensor (1) for mounting to a body for sensing external objects, the sensor comprising a dielectric substrate (2) having front and rear major surfaces which, in use of the sensor, face respectively outward from and towards the body; a sensor conductor (3) on the front major surface; and a guard conductor on at least one of the major surfaces to provide an electrical shield for the sensor conductor; and (ii) a cable (16) for transmitting electrical signals from the sensor (1) to an electronic control unit; the cable comprising a dielectric film substrate having, on a first major surface thereof, a first electrical conductor (13) that is connected to the sensor conductor (3) for transmitting electrical signals therefrom and, on both major surfaces thereof, an electrically-conductive layer (14) that is connected to the guard conductor to provide an electrical shield for the said first conductor (13).