A medicament delivery device (100; 300; 400) comprises a chassis (124), a drive element (166) for driving a stopper (22) to expel the medicament through a cannula (144). A carrier (126) is arranged for movement with respect to the chassis (124). Insertion means (130, 202) biases the carrier (126) in an insertion direction. A control part (132) is biased for rotation with respect to the carrier (126). A locking element (176) prevents rotation of the control part (132) in an initial state. The locking element (176) is coupled to the drive element (166) such that the control part (132) is released for rotation when the drive element (166) reaches an activation position during a delivery stroke. Rotation of the control part (132) through a predetermined angle causes decoupling of the insertion means (130, 202) from the carrier (126) to allow movement of the carrier (126) in a retraction direction after the end of the delivery stroke.