A medicament delivery device comprising: a generally tubular elongated housing having a distal end and a proximal end, the proximal end being arranged with a central passage; a plunger rod, - a drive spring operably arranged to the plunger rod, - an actuator comprising a holding member releasably engaged to the plunger rod for holding said plunger rod with said drive spring in a tensioned state, - a rotator having a generally tubular shape, the rotator being operably connected and movable relative to said actuator and configured to interact with said holding member for holding said holding member in engagement with the plunger rod, - an activator extending through the central passage of the proximal end of the housing and operably connected to said rotator, characterized by the activator being configured to rotate and subsequently linearly displace the rotator in relation to the actuator such that said holding member is released from the plunger rod so that the plunger rod is free to move in the proximal direction due to the force of the drive spring so that a dose of medicament is expelled, wherein said actuator is arranged with a guide surface on which said rotator rests when rotated from a first position to a second position, wherein said rotator is arranged with a cut-out, in which said guide surface can enter in the second position for allowing the subsequently linear displacement of the rotator in relation to the actuator, wherein the activator comprises a proximal tubular part and two distally directed arms extending from the tubular part, with inwardly directed protrusions arranged at the distal end of the arms, wherein said rotator comprises first guide ridges (42 i) that cooperate with the protrusions of the activator, which first guide ridges (42 i) are inclined in relation to a longitudinal direction, and on which first guide ridges (42 i) said activator acts for rotating said rotator from the first position to the second position, wherein said activator is a medicament delivery member guard. a generally tubular elongated housing having a distal end and a proximal end, the proximal end being arranged with a central passage; a plunger rod, - a drive spring operably arranged to the plunger rod, - an actuator comprising a holding member releasably engaged to the plunger rod for holding said plunger rod with said drive spring in a tensioned state, - a rotator having a generally tubular shape, the rotator being operably connected and movable relative to said actuator and configured to interact with said holding member for holding said holding member in engagement with the plunger rod, - an activator extending through the central passage of the proximal end of the housing and operably connected to said rotator, characterized by the activator being configured to rotate and subsequently linearly displace the rotator in relation to the actuator such that said holding member is released from the plunger rod so that the plunger rod is free to move in the proximal direction due to the force of the drive spring so that a dose of medicament is expelled, - a drive spring operably arranged to the plunger rod, - an actuator comprising a holding member releasably engaged to the plunger rod for holding said plunger rod with said drive spring in a tensioned state, - a rotator having a generally tubular shape, the rotator being operably connected and movable relative to said actuator and configured to interact with said holding member for holding said holding member in engagement with the plunger rod, - an activator extending through the central passage of the proximal end of the housing and operably connected to said rotator, characterized by the activator being configured to rotate and subsequently linearly displace the rotator in relation to the actuator such that said holding member is released from the plunger rod so that the plunger rod is free to move in the proximal direction due to the force of the drive spring so that a dose of medicament is expelled, wherein said actuator is arranged with a guide surface on which said rotator rests when rotated from a first position to a second position, wherein said rotator is arranged with a cut-out, in which said guide surface can enter in the second position for allowing the subsequently linear displacement of the rotator in relation to the actuator, wherein the activator comprises a proximal tubular part and two distally directed arms extending from the tubular part, with inwardly directed protrusions arranged at the distal end of the arms, wherein said rotator comprises first guide ridges (42 i) that cooperate with the protrusions of the activator, which first guide ridges (42 i) are inclined in relation to a longitudinal direction, and on which first guide ridges (42 i) said activator acts for rotating said rotator from the first position to the second position, wherein said activator is a medicament delivery member guard.