Abstract: A power cut-off circuit comprises a voltage monitoring circuit and an over-ride circuit (25), the voltage monitoring circuit comparing a portion of the battery voltage with a fixed reference voltage by way of a comparator (26) which, upon change of state, de-enegizes a relay coil of a relay (14) and thereby disconnects the power to most of the vehicle, but not to the starter motor circuit (11), and the override circuit (25) monitors override inputs in response to override conditions, and re-energizes the relay coil in response to an override input, in turn restoring the previously disconnected power.