An inhaler for delivery of a medicament by inhalation, the inhaler comprising: a drive mechanism comprising a canister drive for receiving a canister of medicament, a biasing means, and a trigger mechanism; the trigger mechanism comprising: a latch having: a locked position in which it contacts the canister drive to prevent linear movement of the canister drive and holds the biasing means in a loaded configuration; and an unlocked position in which the latch is disengaged from the canister drive and releases the biasing means from the loaded configuration to drive the canister drive from a rest position to an actuated position; and a blocker having: a blocking position in which it contacts the latch to block movement thereof from the locked position to the unlocked position; and a rotated position in which the blocker is disengaged from the latch and allows movement of the latch from the locked position to the unlocked position; and the blocker is rotatable in response to a force applied to the blocker; and wherein the inhaler further comprises a blocker spring for biasing the blocker into the blocking position; the inhaler further comprises a chassis for at least partially receiving at least one or more of the canister drive, the biasing means, the latch and the blocker; characterized in that the blocker spring is integrally formed with the chassis, preferably comprising an elongate protrusion with one end affixed to the chassis and the other end free from the chassis to enable flexing of the free end of the blocker spring, the free end configured for abutting a portion of the blocker. a drive mechanism comprising a canister drive for receiving a canister of medicament, a biasing means, and a trigger mechanism; the trigger mechanism comprising: a latch having: a locked position in which it contacts the canister drive to prevent linear movement of the canister drive and holds the biasing means in a loaded configuration; and an unlocked position in which the latch is disengaged from the canister drive and releases the biasing means from the loaded configuration to drive the canister drive from a rest position to an actuated position; and a blocker having: a blocking position in which it contacts the latch to block movement thereof from the locked position to the unlocked position; and a rotated position in which the blocker is disengaged from the latch and allows movement of the latch from the locked position to the unlocked position; and a latch having: a locked position in which it contacts the canister drive to prevent linear movement of the canister drive and holds the biasing means in a loaded configuration; and an unlocked position in which the latch is disengaged from the canister drive and releases the biasing means from the loaded configuration to drive the canister drive from a rest position to an actuated position; and a locked position in which it contacts the canister drive to prevent linear movement of the canister drive and holds the biasing means in a loaded configuration; and an unlocked position in which the latch is disengaged from the canister drive and releases the biasing means from the loaded configuration to drive the canister drive from a rest position to an actuated position; and a blocker having: a blocking position in which it contacts the latch to block movement thereof from the locked position to the unlocked position; and a rotated position in which the blocker is disengaged from the latch and allows movement of the latch from the locked position to the unlocked position; and a blocking position in which it contacts the latch to block movement thereof from the locked position to the unlocked position; and a rotated position in which the blocker is disengaged from the latch and allows movement of the latch from the locked position to the unlocked position; and the blocker is rotatable in response to a force applied to the blocker; and wherein the inhaler further comprises a blocker spring for biasing the blocker into the blocking position; the inhaler further comprises a chassis for at least partially receiving at least one or more of the canister drive, the biasing means, the latch and the blocker; characterized in that the blocker spring is integrally formed with the chassis, preferably comprising an elongate protrusion with one end affixed to the chassis and the other end free from the chassis to enable flexing of the free end of the blocker spring, the free end configured for abutting a portion of the blocker.