A security device (10, 22) for an electrically powered device which has a casing, such as an electrical tool, comprising: a control means which is either mounted in a power plug or power cable, or retrofittable to the electrically powered device by mounting in the power plug or power cable, an immobilising circuit for immobilising the electrically powered device, the immobilising circuit either being positioned within the casing of the electrically powered device or retrofittable within the casing; and a power cable connected between the control means and the immobilising circuit, the power cable being adapted to supply power to the electrically powered device, and the immobilising circuit being controlled by the control means, characterised in that the security device includes a remote location-tracking circuit which is either mounted in the power plug or power cable, or retrofittable to the electrically powered device by mounting in the power plug or power cable; the immobilising circuit is a power shut-down circuit for shutting down power to the electrically powered device, the power shut-down circuit including a shut-off relay; the power cable is a 5-core power cable including an earth, live and neutral cores for powering the electrically powered device, and DC positive and negative cores for powering the shut-off relay; and in use, if the remote location-tracking circuit is removed from the electrically powered device by severing the power cable into a first severed power cable portion with the control means and power plug and a second severed power cable portion with the power shut-down circuit and electrically powered device, thereby disconnecting the control means from the power shut-down circuit, the power shut-down circuit is configured to automatically to shut down the power supply to the electrically powered device via the shut-off relay until the first severed power cable portion is correctly re-wired to the second severed power cable portion and thereby reconnecting the control means to the power shut-down circuit. a control means which is either mounted in a power plug or power cable, or retrofittable to the electrically powered device by mounting in the power plug or power cable, an immobilising circuit for immobilising the electrically powered device, the immobilising circuit either being positioned within the casing of the electrically powered device or retrofittable within the casing; and a power cable connected between the control means and the immobilising circuit, the power cable being adapted to supply power to the electrically powered device, and the immobilising circuit being controlled by the control means, characterised in that the security device includes a remote location-tracking circuit which is either mounted in the power plug or power cable, or retrofittable to the electrically powered device by mounting in the power plug or power cable; the immobilising circuit is a power shut-down circuit for shutting down power to the electrically powered device, the power shut-down circuit including a shut-off relay; the power cable is a 5-core power cable including an earth, live and neutral cores for powering the electrically powered device, and DC positive and negative cores for powering the shut-off relay; and in use, if the remote location-tracking circuit is removed from the electrically powered device by severing the power cable into a first severed power cable portion with the control means and power plug and a second severed power cable portion with the power shut-down circuit and electrically powered device, thereby disconnecting the control means from the power shut-down circuit, the power shut-down circuit is configured to automatically to shut down the power supply to the electrically powered device via the shut-off relay until the first severed power cable portion is correctly re-wired to the second severed power cable portion and thereby reconnecting the control means to the power shut-down circuit.