A lockable trigger mechanism for an electrical device, comprising: a housing; a trigger for biased movement relative to the housing; an actuator movably mounted to the housing such that in response to operation of the trigger, the actuator is movable along a movement axis from an OFF position inwardly of the housing towards an ON position, and movable along the movement axis from the ON position in a direction outwardly of the housing towards the OFF position; an electrical switch unit mounted to the housing for activation in response to movement of the actuator along the movement axis between its ON and OFF positions to close and open an electrical circuit of the electrical device respectively; and a locking mechanism comprising a first locking member, a second locking member and a biasing member configured for biasing movement of the first locking member relative to the second locking member.