A medicament delivery device comprising: - a generally elongated housing having opposite distal and proximal ends, and adapted to store a medicament container assembly - a drive assembly disposed in said housing and configured to act on said medicament container assembly for expelling a dose of medicament; and - an actuation assembly operably connected to said drive assembly for activating said drive assembly, wherein said drive assembly comprises: - a guard member being movable in relation to the housing and having a proximal housing part protruding from the proximal end of the housing wherein the guard member has a protrusion extending distally on an outer surface, wherein the protrusion is arranged to cooperate with a locking ledge in a first locking position; - and an actuator member disposed in said housing and being operable through the housing; wherein the actuation assembly further comprises a rotator barrel rotatably disposed between the guard member and the actuator member, wherein the locking ledge is arranged on the inner surface of a proximally directed tongue, which tongue is attached to a rotator barrel in the form of a generally tubular rotator barrel, where the rotator barrel is arranged rotatable inside said housing, wherein said rotator barrel is configured to be rotated by the guard member when the guard member is pressed against a delivery site between the first locking position in which the rotator barrel is blocking the actuator member and a released position in which the rotator barrel allows the actuator member to be operated, wherein the rotator barrel is arranged with proximally directed inclined surfaces which are cooperating with distally directed inclined surfaces arranged on a tongue of the guard member in the released position; and wherein said rotator barrel is further configured to be rotated by an inclined surface of the actuator member cooperating with an inclined surface of the rotator barrel between the released position and a second locking position in which a proximally directed lock tab 35 of the rotator barrel is blocking the protrusion of the guard member after said guard member is removed from the delivery site; and wherein the rotator barrel is configured to be rotated in relation to the housing by the guard member and by the actuator member. - a generally elongated housing having opposite distal and proximal ends, and adapted to store a medicament container assembly - a drive assembly disposed in said housing and configured to act on said medicament container assembly for expelling a dose of medicament; and - an actuation assembly operably connected to said drive assembly for activating said drive assembly, wherein said drive assembly comprises: - a guard member being movable in relation to the housing and having a proximal housing part protruding from the proximal end of the housing wherein the guard member has a protrusion extending distally on an outer surface, wherein the protrusion is arranged to cooperate with a locking ledge in a first locking position; - and an actuator member disposed in said housing and being operable through the housing; wherein the actuation assembly further comprises a rotator barrel rotatably disposed between the guard member and the actuator member, - a guard member being movable in relation to the housing and having a proximal housing part protruding from the proximal end of the housing wherein the guard member has a protrusion extending distally on an outer surface, wherein the protrusion is arranged to cooperate with a locking ledge in a first locking position; - and an actuator member disposed in said housing and being operable through the housing; wherein the actuation assembly further comprises a rotator barrel rotatably disposed between the guard member and the actuator member, wherein the locking ledge is arranged on the inner surface of a proximally directed tongue, which tongue is attached to a rotator barrel in the form of a generally tubular rotator barrel, where the rotator barrel is arranged rotatable inside said housing, wherein said rotator barrel is configured to be rotated by the guard member when the guard member is pressed against a delivery site between the first locking position in which the rotator barrel is blocking the actuator member and a released position in which the rotator barrel allows the actuator member to be operated, wherein the rotator barrel is arranged with proximally directed inclined surfaces which are cooperating with distally directed inclined surfaces arranged on a tongue of the guard member in the released position; and wherein said rotator barrel is further configured to be rotated by an inclined surface of the actuator member cooperating with an inclined surface of the rotator barrel between the released position and a second locking position in which a proximally directed lock tab 35 of the rotator barrel is blocking the protrusion of the guard member after said guard member is removed from the delivery site; and wherein the rotator barrel is configured to be rotated in relation to the housing by the guard member and by the actuator member.