An anti-theft device for a vehicle which includes a power plant and a drivetrain, the power plant being drivingly connected to the drivetrain in order to propel the vehicle, characterized in that the anti-theft device includes: a locking member which is mounted adjacent to the drivetrain, downstream of the power plant, and which is movable relative to the drivetrain between an open position in which a driveshaft or transmission of the drivetrain is permitted to move relative to the locking member and an engaged or locked position in which the locking member prevents displacement of the driveshaft or transmission relative to the locking member by engaging the drivetrain or transmission thus preventing rotation thereof and locking it in position hence immobilising the vehicle; an actuator which is configured to displace the locking member relative to the drivetrain from one of its open or locked positions to the other; an electronic control unit which is communicatively linked to the actuator and is configured to receive a signal indicative of whether or not the drivetrain is in motion; and a wireless communication module which is communicatively linked to the electronic control unit and is configured to communicate with a remote control, the anti-theft device accordingly being remotely actuatable, further characterized in that the electronic control unit is further configured to actuate the actuator in order to move the locking member into its locked position provided that the vehicle is not in motion or is moving at a rate which is below a predetermined threshold value, and characterized in that the electronic control unit, actuator and locking member are housed within a retro-fittable tamper-proof casing, downstream of the power plant, further characterized in that the locking member includes a locking pawl which is pivotally displaceable relative to a toothed rotor of the drivetrain of the vehicle, the toothed rotor being mounted to the driveshaft of the vehicle beyond a clutch and characterized in that the wireless communication module includes any one or more of a satellite tracking unit, a satellite transceiver, a Bluetooth module, a RFID transceiver, a GSM-enabled module and a Wi-Fi module such that signals and commands can be sent to and received from the device via a satellite and/or cellular communication network via the wireless communication module which is coupled to the electronic control unit, further characterized in that a first signal received by the electronic control unit indicative of whether or not power to the power plant is cut off, is derived from a vehicle ignition switch and that the communication module enables remote control of the device even when an owner is not in close proximity to the vehicle, such that, in the event that the vehicle has been stolen, the owner can still prime the device to lock it as soon as the ignition has been turned off. a locking member which is mounted adjacent to the drivetrain, downstream of the power plant, and which is movable relative to the drivetrain between an open position in which a driveshaft or transmission of the drivetrain is permitted to move relative to the locking member and an engaged or locked position in which the locking member prevents displacement of the driveshaft or transmission relative to the locking member by engaging the drivetrain or transmission thus preventing rotation thereof and locking it in position hence immobilising the vehicle; an actuator which is configured to displace the locking member relative to the drivetrain from one of its open or locked positions to the other; an electronic control unit which is communicatively linked to the actuator and is configured to receive a signal indicative of whether or not the drivetrain is in motion; and a wireless communication module which is communicatively linked to the electronic control unit and is configured to communicate with a remote control, the anti-theft device accordingly being remotely actuatable, further characterized in that the electronic control unit is further configured to actuate the actuator in order to move the locking member into its locked position provided that the vehicle is not in motion or is moving at a rate which is below a predetermined threshold value, and characterized in that the electronic control unit, actuator and locking member are housed within a retro-fittable tamper-proof casing, downstream of the power plant, further characterized in that the locking member includes a locking pawl which is pivotally displaceable relative to a toothed rotor of the drivetrain of the vehicle, the toothed rotor being mounted to the driveshaft of the vehicle beyond a clutch and characterized in that the wireless communication module includes any one or more of a satellite tracking unit, a satellite transceiver, a Bluetooth module, a RFID transceiver, a GSM-enabled module and a Wi-Fi module such that signals and commands can be sent to and received from the device via a satellite and/or cellular communication network via the wireless communication module which is coupled to the electronic control unit, further characterized in that a first signal received by the electronic control unit indicative of whether or not power to the power plant is cut off, is derived from a vehicle ignition switch and that the communication module enables remote control of the device even when an owner is not in close proximity to the vehicle, such that, in the event that the vehicle has been stolen, the owner can still prime the device to lock it as soon as the ignition has been turned off.