A breath-responsive inhaler having a trigger mechanism for triggering delivery of a medicament to a user, a trigger mechanism chassis for locating the trigger mechanism within the inhaler, and an air flow path through which the user inhales, the trigger mechanism including: a medicament source, having a primed position in which the inhaler is primed for use and an actuated position in which the medicament source is actuated to dispense a dose of medicament, the trigger mechanism further comprising: a toggle mechanism for selectively permitting movement of the source from its primed position to its actuated position, the toggle mechanism comprising: a vane positioned in the air flow path, the vane being pivoted about a vane pivot, and a toggle link pivotally mounted on the vane at a toggle link pivot, wherein the trigger mechanism is triggered by movement of the vane upon inhalation of the user to move the toggle mechanism between a primed condition in which the medicament source is maintained in its primed position by cooperation with the toggle mechanism and an actuated condition in which the toggle mechanism is disengaged from cooperation with the medicament source, the trigger mechanism further comprising an actuation arm for engaging the medicament source, the actuation arm having a primed position in which the toggle mechanism is in its primed condition, and having an actuated position in which the toggle mechanism is in its actuated condition, wherein in said primed condition the actuation arm is maintained in its primed position by engagement with the toggle mechanism, and in said actuated condition the toggle mechanism is disengaged from the actuation arm to permit the actuation arm to move to its actuated position. a medicament source, having a primed position in which the inhaler is primed for use and an actuated position in which the medicament source is actuated to dispense a dose of medicament, the trigger mechanism further comprising: a toggle mechanism for selectively permitting movement of the source from its primed position to its actuated position, the toggle mechanism comprising: a vane positioned in the air flow path, the vane being pivoted about a vane pivot, and a toggle link pivotally mounted on the vane at a toggle link pivot, wherein the trigger mechanism is triggered by movement of the vane upon inhalation of the user to move the toggle mechanism between a primed condition in which the medicament source is maintained in its primed position by cooperation with the toggle mechanism and an actuated condition in which the toggle mechanism is disengaged from cooperation with the medicament source, the trigger mechanism further comprising an actuation arm for engaging the medicament source, the actuation arm having a primed position in which the toggle mechanism is in its primed condition, and having an actuated position in which the toggle mechanism is in its actuated condition, wherein in said primed condition the actuation arm is maintained in its primed position by engagement with the toggle mechanism, and in said actuated condition the toggle mechanism is disengaged from the actuation arm to permit the actuation arm to move to its actuated position. a toggle mechanism for selectively permitting movement of the source from its primed position to its actuated position, the toggle mechanism comprising: a vane positioned in the air flow path, the vane being pivoted about a vane pivot, and a toggle link pivotally mounted on the vane at a toggle link pivot, wherein the trigger mechanism is triggered by movement of the vane upon inhalation of the user to move the toggle mechanism between a primed condition in which the medicament source is maintained in its primed position by cooperation with the toggle mechanism and an actuated condition in which the toggle mechanism is disengaged from cooperation with the medicament source, the trigger mechanism further comprising an actuation arm for engaging the medicament source, the actuation arm having a primed position in which the toggle mechanism is in its primed condition, and having an actuated position in which the toggle mechanism is in its actuated condition, wherein in said primed condition the actuation arm is maintained in its primed position by engagement with the toggle mechanism, and in said actuated condition the toggle mechanism is disengaged from the actuation arm to permit the actuation arm to move to its actuated position. a vane positioned in the air flow path, the vane being pivoted about a vane pivot, and a toggle link pivotally mounted on the vane at a toggle link pivot, wherein the trigger mechanism is triggered by movement of the vane upon inhalation of the user to move the toggle mechanism between a primed condition in which the medicament source is maintained in its primed position by cooperation with the toggle mechanism and an actuated condition in which the toggle mechanism is disengaged from cooperation with the medicament source, the trigger mechanism further comprising an actuation arm for engaging the medicament source, the actuation arm having a primed position in which the toggle mechanism is in its primed condition, and having an actuated position in which the toggle mechanism is in its actuated condition, wherein in said primed condition the actuation arm is maintained in its primed position by engagement with the toggle mechanism, and in said actuated condition the toggle mechanism is disengaged from the actuation arm to permit the actuation arm to move to its actuated position.