A method of and device for immobilising a motor vehicle having a foot actuated brake pedal affixed at the end of a pedal arm. A pedal clasping portion of the immobilisation device is hooked around the brake pedal and a rigid strut portion slides from an elongate body portion where it is locked in such extended position to prevent depression of the brake pedal to its actuating position. The pedal clasping portion has the form of a deep channel firmly affixed to the elongate body portion of the device and may have a cutout in one of the flanges through which the pedal arm passes.